Methods for the synthesis of astaxanthin

ABSTRACT

A method used for synthesizing intermediates for use in the synthesis of carotenoids and carotenoid analogs, and/or carotenoid derivatives. In some embodiments, the invention includes methods for synthesizing optically active intermediates useful for the synthesis of optically active carotenoids. Synthesis of optically active carotenoids, in one embodiment, may be accomplished by forming an optically active dihydroxy ketone intermediate from ketoisopherone. The optically active dihydroxy ketone intermediate may be converted into optically active astaxanthin derivatives.

PRIORTY CLAIM

This application claims priority to U.S. Provisional Patent ApplicationNo. 60/615,032 entitiled “Methods for Synthesis of Carotenoids,Including Analogs, Derivatives, and Synthetic and BiologicalIntermediates” filed on Oct. 1, 2004; U.S. Provisional PatentApplication No. 60/675,957 entitiled “Methods for Synthesis ofCarotenoids, Including Analogs, Derivatives, and Synthetic andBiological Intermediates” filed on Apr. 29, 2005; U.S. ProvisionalPatent Application No. 60/691,518 entitiled “Methods for Synthesis ofCarotenoids, Including Analogs, Derivatives, and Synthetic andBiological Intermediates” filed on Jun. 17, 2005; U.S. ProvisionalPatent Application No. 60/692,682 entitiled “Methods for Synthesis ofCarotenoids, Including Analogs, Derivatives, and Synthetic andBiological Intermediates” filed on Jun. 21, 2005; U.S. ProvisionalPatent Application No. 60/699,653 entitiled “Methods for Synthesis ofCarotenoids, Including Analogs, Derivatives, and Synthetic andBiological Intermediates” filed on Jul. 15, 2005; U.S. ProvisionalPatent Application No. 60/702,380 entitiled “Methods for Synthesis ofCarotenoids, Including Analogs, Derivatives, and Synthetic andBiological Intermediates” filed on Jul. 26, 2005; and U.S. ProvisionalPatent Application No. 60/712,350 entitiled “Methods for Synthesis ofCarotenoids, Including Analogs, Derivatives, and Synthetic andBiological Intermediates” filed on Aug. 30, 2005.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention generally relates to the fields of medicinal and syntheticchemistry. More specifically, the invention relates to the synthesis anduse of carotenoids, including analogs, derivatives, and intermediates.

2. Description of the Relevant Art

Carotenoids are a group of natural pigments produced principally byplants, yeast, and microalgae. The family of related compounds nownumbers greater than 700 described members, exclusive of Z and Eisomers. At least fifty (50) carotenoids have been found in human seraor tissues. Humans and other animals cannot synthesize carotenoids denovo and must obtain them from their diet. All carotenoids share commonchemical features, such as a polyisoprenoid structure, a long polyenechain forming the chromophore, and near symmetry around the centraldouble bond. Tail-to-tail linkage of two C₂₀ geranyl diphosphatemolecules produces the parent C₄₀ carbon skeleton. Carotenoids withoutoxygenated functional groups are called “carotenes”, reflecting theirhydrocarbon nature; oxygenated carotenes are known as “xanthophylls.”Cyclization at one or both ends of the molecule yields 7 identified endgroups (illustrative structures shown in FIG. 1).

Documented carotenoid functions in nature include light-harvesting,photoprotection, and protective and sex-related coloration inmicroscopic organisms, mammals, and birds, respectively. A relativelyrecent observation has been the protective role of carotenoids againstage-related diseases in humans as part of a complex antioxidant networkwithin cells. This role is dictated by the close relationship betweenthe physicochemical properties of individual carotenoids and their invivo functions in organisms. The long system of alternating double andsingle bonds in the central part of the molecule (delocalizing theπ-orbital electrons over the entire length of the polyene chain) confersthe distinctive molecular shape, chemical reactivity, andlight-absorbing properties of carotenoids. Additionally, isomerismaround C═C double bonds yields distinctly different molecular structuresthat may be isolated as separate compounds (known as Z (“cis”) and E(“trans”), or geometric, isomers). Of the more than 700 describedcarotenoids, an even greater number of the theoretically possible mono-Zand poly-Z isomers are sometimes encountered in nature. The presence ofa Z double bond creates greater steric hindrance between nearby hydrogenatoms and/or methyl groups, so that Z isomers are generally less stablethermodynamically, and more chemically reactive, than the correspondingall-E form. The all-E configuration is an extended, linear, and rigidmolecule. Z-isomers are, by contrast, not simple, linear molecules (theso-called “bent-chain” isomers). The presence of any Z in the polyenechain creates a bent-chain molecule. The tendency of Z-isomers tocrystallize or aggregate is much less than all-E, and Z isomers maysometimes be more readily solubilized, absorbed, and transported in vivothan their all-E counterparts. This has important implications forenteral (e.g., oral) and parenteral (e.g., intravenous, intra-arterial,intramuscular, intraperitoneal, intracoronary, and subcutaneous) dosingin mammals.

Carotenoids with chiral centers may exist either as the R (rectus) or S(sinister) configurations. As an example, astaxanthin (with 2 chiralcenters at the 3 and 3′ carbons) may exist as 3 possible stereoisomers:35, 3′S; 3R, 3′S and 3S, 3′R (identical meso forms); or 3R, 3′R. Therelative proportions of each of the stereoisomers may vary by naturalsource. For example, Haematococcus pluvialis microalgal meal is 99% 35,3′S astaxanthin, and is likely the predominant human evolutionary sourceof astaxanthin. Krill (3R,3′R) and yeast sources yield differentstereoisomer compositions than the microalgal source. Syntheticastaxanthin, produced by large manufacturers such as Hoffmann-LaRocheAG, Buckton Scott (USA), or BASF AG, are provided as defined geometricisomer mixtures of a 1:2:1 stereoisomer mixture (3S, 3′S; 3R, 3′S,(meso); 3R, 3′R) of non-esterified, free astaxanthin. Natural sourceastaxanthin from salmonid fish is predominantly a single stereoisomer(3S,3′S), but does contain a mixture of geometric isomers. Astaxanthinfrom the natural source Haematococcus pluvialis may contain nearly 50% Zisomers. As stated above, the Z conformational change may lead to ahigher steric interference between the two parts of the carotenoidmolecule, rendering it less stable, more reactive, and more susceptibleto reactivity at low oxygen tensions. In such a situation, in relationto the all-E form, the Z forms: (1) may be degraded first; (2) maybetter suppress the attack of cells by reactive oxygen species such assuperoxide anion; and (3) may preferentially slow the formation ofradicals. Overall, the Z forms may initially be thermodynamicallyfavored to protect the lipophilic portions of the cell and the cellmembrane from destruction. It is important to note, however, that theall-E form of astaxanthin, unlike β-carotene, retains significant oralbioavailability as well as antioxidant capacity in the form of itsdihydroxy- and diketo-substitutions on the β-ionone rings, and has beendemonstrated to have increased efficacy over β-carotene in most studies.The all-E form of astaxanthin has also been postulated to have the mostmembrane-stabilizing effect on cells in vivo. Therefore, it is likelythat the all-E form of astaxanthin in natural and synthetic mixtures ofstereoisomers is also extremely important in antioxidant mechanisms, andmay be the form most suitable for particular pharmaceuticalpreparations.

The antioxidant mechanism(s) of carotenoids, (e.g., astaxanthin),includes singlet oxygen quenching, direct radical scavenging, and lipidperoxidation chain-breaking. The polyene chain of the carotenoid absorbsthe excited energy of singlet oxygen, effectively stabilizing the energytransfer by delocalization along the chain, and dissipates the energy tothe local environment as heat. Transfer of energy from triplet-statechlorophyll (in plants) or other porphyrins and proto-porphyrins (inmammals) to carotenoids occurs much more readily than the alternativeenergy transfer to oxygen to form the highly reactive and destructivesinglet oxygen (¹O₂). Carotenoids may also accept the excitation energyfrom singlet oxygen if any should be formed in situ, and again dissipatethe energy as heat to the local environment. This singlet oxygenquenching ability has significant implications in cardiac ischemia,macular degeneration, porphyria, and other disease states in whichproduction of singlet oxygen has damaging effects. In the physicalquenching mechanism, the carotenoid molecule may be regenerated (mostfrequently), or be lost. Carotenoids are also excellent chain-breakingantioxidants, a mechanism important in inhibiting the peroxidation oflipids. Astaxanthin can donate a hydrogen (H) to the unstablepolyunsaturated fatty acid (PUFA) radical, stopping the chain reaction.Peroxyl radicals may also, by addition to the polyene chain ofcarotenoids, be the proximate cause for lipid peroxide chaintermination. The appropriate dose of astaxanthin has been shown tocompletely suppress the peroxyl radical chain reaction in liposomesystems. Astaxanthin shares with vitamin E this dual antioxidant defensesystem of singlet oxygen quenching and direct radical scavenging, and inmost instances (and particularly at low oxygen tension in vivo) issuperior to vitamin E as a radical scavenger and physical quencher ofsinglet oxygen.

Carotenoids, (e.g., astaxanthin), are potent direct radical scavengersand singlet oxygen quenchers and possess all the desirable qualities ofsuch therapeutic agents for inhibition or amelioration ofischemia-reperfusion injury. Synthesis of novel carotenoid derivativeswith “soft-drug” properties (i.e. active as antioxidants in thederivatized form), with physiologically relevant, cleavable linkages topro-moieties, can generate significant levels of free carotenoids inboth plasma and solid organs. In the case of non-esterified, freeastaxanthin, this is a particularly useful embodiment (characteristicsspecific to non-esterified, free astaxanthin below):

-   -   Lipid soluble in natural form; may be modified to become more        water soluble;    -   Molecular weight of 597 Daltons (size<600 daltons (Da) readily        crosses the blood brain barrier, or BBB);    -   Long polyene chain characteristic of carotenoids effective in        singlet oxygen quenching and lipid peroxidation chain breaking;        and    -   No pro-vitamin A activity in mammals (eliminating concerns of        hypervitaminosis A and retinoid toxicity in humans).

The administration of antioxidants which are potent singlet oxygenquenchers and direct radical scavengers, particularly of superoxideanion, should limit hepatic fibrosis and the progression to cirrhosis byaffecting the activation of hepatic stellate cells early in thefibrogenetic pathway. Reduction in the level of “Reactive OxygenSpecies” (ROS) by the administration of a potent antioxidant cantherefore be crucial in the prevention of the activation of both“hepatic stellate cells” (HSC) and Kupffer cells. This protectiveantioxidant effect appears to be spread across the range of potentialtherapeutic antioxidants, including water-soluble (e.g., vitamin C,glutathione, resveratrol) and lipophilic (e.g., vitamin E, β-carotene,astaxanthin) agents. Therefore, a co-antioxidant derivative strategy inwhich water-soluble and lipophilic agents are combined synthetically isa particularly useful embodiment. Examples of uses of carotenoidderivatives and analogs are illustrated in U.S. patent application Ser.No. 10/793,671 filed on Mar. 4, 2004, entitled “CAROTENOID ETHER ANALOGSOR DERIVATIVES FOR THE INHIBITION AND AMELIORATION OF DISEASE” toLockwood et al. published on Jan. 13, 2005, as Publication No.US-2005-0009758 and PCT International Application NumberPCT/US2003/023706 filed on Jul. 29, 2003, entitled “STRUCTURALCAROTENOID ANALOGS FOR THE INHIBITION AND AMELIORATION OF DISEASE” toLockwood et al. (International Publication Number WO 2004/011423 A2,published on Feb. 5, 2004) both of which are incorporated by referenceas if fully set forth herein.

Vitamin E is generally considered the reference antioxidant. Whencompared with vitamin E, carotenoids are more efficient in quenchingsinglet oxygen in homogeneous organic solvents and in liposome systems.They are better chain-breaking antioxidants as well in liposomalsystems. They have demonstrated increased efficacy and potency in vivo.They are particularly effective at low oxygen tension, and in lowconcentration, making them extremely effective agents in diseaseconditions in which ischemia is an important part of the tissue injuryand pathology. These carotenoids also have a natural tropism for theheart and liver after oral administration. Therefore, therapeuticadministration of carotenoids should provide a greater benefit inlimiting fibrosis than vitamin E.

Problems related to the use of some carotenoids and structuralcarotenoid analogs or derivatives include: (1) the complex isomericmixtures, including non-carotenoid contaminants, provided in natural andsynthetic sources leading to costly increases in safety and efficacytests required by such agencies as the FDA; (2) limited bioavailabilityupon administration to a subject; and (3) the differential induction ofcytochrome P450 enzymes (this family of enzymes exhibitsspecies-specific differences which must be taken into account whenextrapolating animal work to human studies). Selection of theappropriate analog or derivative and isomer composition for a particularapplication increases the utility of carotenoid analogs or derivativesfor the uses defined herein.

Synthesis of an appropriate analog or derivative and isomer compositionrequires a supply of starting materials (e.g., carotenoids, carotenoidsynthetic intermediates). Any new synthetic route which is moreefficient to a carotenoid analog or derivative and/or syntheticintermediate would be beneficial. More efficient synthetic routes wouldprovide a more stable source of starting materials (e.g., carotenoids)which may be difficult or expensive to extract from natural sources.Synthetic routes to natural products may facilitate the synthesis ofanalogs and derivatives of the natural products.

SUMMARY

A synthetic route to a carotenoid, carotenoid analog or derivativeand/or synthetic intermediate is presented.

In some embodiments, methods and reactions described herein may be usedto synthesize naturally-occurring carotenoids. Naturally-occurringcarotenoids may include astaxanthin as well as other carotenoidsincluding, but not limited to, zeaxanthin, carotenediol, nostoxanthin,crustaxanthin, canthaxanthin, isozeaxanthin, hydroxycanthaxanthin,tetrahydroxy-carotene-dione, lutein, lycophyll, and lycopene.

In one embodiment, a method of making astaxanthin includes: contacting adiketone compound having the structure

where each R is independently alkyl, phenyl, or aryl and where R¹ isalkyl, phenyl, aryl or silyl,with a chiral catalyst, to stereoselectively reduce the ketone to give ahydroxy product having the general structure:

where the “*” represents a chiral carbon atom that exists,predominantly, as a single stereoisomer.

In some embodiments, each R is methyl. The chiral catalyst, in someembodiments, includes a metal and an optically active chiral ligand. Themetal may be any transition metal. In some embodiments, the metal isruthenium.

A chiral catalyst may include ruthenium and an optically active chiralligand. In some embodiments, an optically active chiral ligand is anoptically active amine. Examples of optically active amines include:amino acids, H₂N—CHPh—CHPh—OH, H₂N—CHMe—CHPh—OH, MeHN—CHMe—CHPh—OH,H₂N—CHPh—CHPh—OH, H₂N—CHMe—CHPh—OH, MeHN—CHMe—CHPh—OH, andTsNH—CHPh—CHPh—NH₂.

Use of a chiral catalyst to reduce the diketone starting material maylead to optically active stereoisomers that include the dihydroxy ketonecompound

The dihydroxy ketone may be converted into the unsaturated ketone havingthe structure:

where R¹ is alkyl, phenyl, aryl or silyl, and R² is

The unsaturared ketone may then be converted into an aldehyde reactivecompound having the structure:

where R¹ is is alkyl, phenyl, aryl or silyl; and R³ is PR⁴ ₃, P(O)R⁴ ₃,SO₂R⁴, or M⁺ where R⁴ is alkyl, phenyl, or aryl and M is Li, Na, orMgBr. The aldehyde reactive compound may then be reacted with thedialdehyde having the structure

to form astaxanthin. All stereoisomers of astaxanthin may be selectivelyformed using this method including the 3S, 3′S stereoisomer and the 3R,3′R stereoisomer.

BRIEF DESCRIPTION OF THE DRAWINGS

The above brief description as well as further objects, features andadvantages of the methods and apparatus of the present invention will bemore fully appreciated by reference to the following detaileddescription of presently preferred but nonetheless illustrativeembodiments in accordance with the present invention when taken inconjunction with the accompanying drawings.

FIG. 1 depicts a graphic representation of several examples of “parent”carotenoid structures as found in nature.

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof are shown by way ofexample in the drawings and may herein be described in detail. Thedrawings may not be to scale. It should be understood, however, that thedrawings and detailed description thereto are not intended to limit theinvention to the particular form disclosed, but on the contrary, theintention is to cover all modifications, equivalents and alternativesfalling within the spirit and scope of the present invention as definedby the appended claims.

DETAILED DESCRIPTION

Compounds described herein embrace both racemic and optically activecompounds. Chemical structures depicted herein which do not designatespecific stereochemistry are intended to embrace all possiblestereochemistries.

It will be appreciated by those skilled in the art that compounds havingone or more chiral center(s) may exist in and be isolated in opticallyactive and racemic forms. Some compounds may exhibit polymorphism. It isto be understood that the present invention encompasses any racemic,optically-active, polymorphic, or stereoisomeric form, or mixturesthereof, of a compound. As used herein, the term “single stereoisomer”refers to a compound having one or more chiral center that, while it canexist as two or more stereoisomers, is isolated in greater than about95% excess of one of the possible stereoisomers. As used herein acompound that has one or more chiral centers is considered to be“optically active” when isolated or used as a single stereoisomer.

The following definitions are used, unless otherwise described. Halo, asused herein refers to fluoro, chloro, bromo, or iodo. “Alkyl,” “alkoxy,”etc. denote both straight and branched groups; but reference to anindividual radical such as “propyl” embraces only the straight chainradical, a branched chain isomer such as “isopropyl” being specificallyreferred to.

Specific and preferred values listed below for radicals, substituents,and ranges, are for illustration only; they do not exclude other definedvalues or other values within defined ranges for the radicals andsubstituents. Specifically, “alkyl” includes, but is not limited to:methyl, ethyl, propyl, isopropyl, butyl, iso-butyl, sec-butyl, pentyl,3-pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl,tridecyl, tetradecyl or pentadecyl; “alkenyl” includes but is notlimited to vinyl, 1-propenyl, 2-propenyl, 1-butenyl, 2-butenyl,3-butenyl, 1-pentenyl, 2-pentenyl, 3-pentenyl, 4-pentenyl, 1-hexenyl,2-hexenyl, 3-hexenyl, 4-hexenyl, 5-hexenyl, 1-heptenyl, 2-heptenyl,3-heptenyl, 4-heptenyl, 5-heptenyl, 1-nonenyl, 2-nonenyl, 3-nonenyl,4-nonenyl, 5-nonenyl, 6-nonenyl, 7-nonenyl, 8-nonenyl, 1-decenyl,2-decenyl, 3-decenyl, 4-decenyl, 5-decenyl, 6-decenyl, 7-decenyl,8-decenyl, 9-decenyl; 1-undecenyl, 2-undecenyl, 3-undecenyl,4-undecenyl, 5-undecenyl, 6-undecenyl, 7-undecenyl, 8-undecenyl,9-undecenyl, 10-undecenyl, 1-dodecenyl, 2-dodecenyl, 3-dodecenyl,4-dodecenyl, 5-dodecenyl, 6-dodecenyl, 7-dodecenyl, 8-dodecenyl,9-dodecenyl, 10-dodecenyl, 11-dodecenyl, 1-tridecenyl, 2-tridecenyl,3-tridecenyl, 4-tridecenyl, 5-tridecenyl, 6-tridecenyl, 7-tridecenyl,8-tridecenyl, 9-tridecenyl, 10-tridecenyl, 11-tridecenyl, 12-tridecenyl,1-tetradecenyl, 2-tetradecenyl, 3-tetradecenyl, 4-tetradecenyl,5-tetradecenyl, 6-tetradecenyl, 7-tetradecenyl, 8-tetradecenyl,9-tetradecenyl, 10-tetradecenyl, 11-tetradecenyl, 12-tetradecenyl,13-tetradeceny, 1-pentadecenyl, 2-pentadecenyl, 3-pentadecenyl,4-pentadecenyl, 5-pentadecenyl, 6-pentadecenyl, 7-pentadecenyl,8-pentadecenyl, 9-pentadecenyl, 10-pentadecenyl, 11-pentadecenyl,12-pentadecenyl, 13-pentadecenyl, 14-pentadecenyl; “alkoxy” includes butis not limited to methoxy, ethoxy, propoxy, isopropoxy, butoxy,iso-butoxy, sec-butoxy, pentoxy, 3-pentoxy, hexoxy, heptyloxy, octyloxy,nonyloxy, decyloxy, undecyloxy, dodecyloxy, tridecyloxy, tetradecyloxy,or pentadecyloxy; “cycloalkyl” includes, but is not limited tocyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, orcyclooctyl. “Aryl” includes but is not limited to phenyl, substitutedbenzene, naphthyl, substituted naphthyl, anthracene, or substitutedanthracene.

The synthesis of certain naturally-occurring carotenoids is presentedherein. In some embodiments, methods and reactions described herein maybe used to synthesize naturally-occurring carotenoids.Naturally-occurring carotenoids may include astaxanthin as well as othercarotenoids. Some of the other carotenoids may include carotenoids suchas, for example, zeaxanthin, carotenediol, nostoxanthin, crustaxanthin,canthaxanthin, isozeaxanthin, hydroxycanthaxanthin,tetrahydroxy-carotene-dione, lutein, and lycopene. Carotenoids havingthe general formula (I) below may be synthesized using the methodsdescribed herein.

Where X, Y, and Z are independently —OH or ═O.

The compound of formula I embraces “racemic” (e.g. statistical mixtureof stereoisomers), optically inactive (e.g. meso forms) and opticallyactive (e.g. enantiomeric) compounds. In some embodiments, carotenoidsmay be isolated using methods described herein with an enantiomericexcess of greater than 99%. In some embodiments, carotenoids may beisolated using methods described herein with an enantiomeric excess ofgreater than 95%. In some embodiments, carotenoids may be isolated usingmethods described herein with an enantiomeric excess of greater than90%.

In some embodiments, Z is H, Y is —OH, and X is ═O such that thecarotenoid has the general structure depicted below. The carotenoidbelow is commonly referred to as astaxanthin.

In some embodiments, Z is H, Y is OH, and X is OH such that thecarotenoid has the general structure depicted below. The carotenoidbelow is commonly referred to as crustaxanthin.

In some embodiments, Z is H, Y is H, and X is ═O such that thecarotenoid has the general structure depicted below. The carotenoidbelow is commonly referred to as canthaxanthin.

In some embodiments, Z is H, Y is H, and X is —OH such that thecarotenoid has the general structure depicted below. The carotenoidbelow is commonly referred to as isozeaxanthin.

In some embodiments, Z is OH, Y is H, and X is ═O such that thecarotenoid has the general structure depicted below. The carotenoidbelow is commonly referred to as hydroxycanthaxanthin.

In some embodiments, Z and Y are —OH and X is ═O such that thecarotenoid has the general structure depicted below. The carotenoidbelow is commonly referred to as tetrahydroxy-carotene-dione

In an embodiment, carotenoids may be synthesized using the generalprocess shown in Scheme I below.

Where X, Y, and Z are independently —OH or ═O; where R³ is PR⁴ ₃, SO₂R⁴,or M⁺. R⁴ is alkyl, phenyl, or aryl. M is Li, Na, or MgBr. Coupling oftwo “head units” with the C₁₀-aldehyde yields carotenoid. Coupling maybe accomplished using a Wittig coupling (R³ is PR⁴ ₃), sulphone coupling(R³ is SO₂R⁴), or condensation reaction (R³ is M⁺). The C₁₀ aldehyde iscommercially available. Described herein are various methods ofsynthesizing the appropriate headpiece. The following U.S. patents, allof which are incorporated herein by reference, describe the synthesis ofvarious carotene and carotenoid synthesis intermediates: U.S. Pat. No.4,245,109 to Mayer et al., U.S. Pat. No. 4,283,559 to Broger et al, U.S.Pat. No. 4,585,885 to Bernhard et al., U.S. Pat. No. 4,952,716 to Lukacet al., and U.S. Pat. No. 6,747,177 to Ernst et al.

In one embodiment, a headpiece useful for the synthesis of astaxanthinmay be formed using the process depicted in Scheme II.

While the compounds shown in Scheme II are generally depicted as singlestereoisomers, it should be understood that Scheme II may be used tosynthesize the racemic headpiece. An intermediate in the synthesis ofastaxanthin is shown below as compound 108A.

R¹ may include hydrogen, alkyl, or aryl. R³ may also include any alcoholprotecting groups known to one skilled in the art. Protecting groups mayinclude, but are not limited to, silyl protecting groups such astert-butyldimethylsilane (i.e., TBDMS). In some embodiments, compound108a may be synthesized from commercially available keto-α-isopherone109 having a general formula of

Keto-α-isopherone may be selectively reduced. The more stericallyhindered ketone may be reduced to an alcohol. The more stericallyhindered ketone A may be stereoselectively reduced to an alcohol. Insome embodiments, a complexing reagent may be used to react with theless sterically hindered ketone. In so doing this, the complexing agentmay protect the less sterically hindered ketone B from reacting with areagent (e.g., a reducing agent), thereby directing the reagent to reactwith the more sterically hindered ketone A.

In some embodiments, a complexing agent may also be optically pure orform an optically pure complex with an activating metal, either of whichmay react with the less sterically hindered ketone B, such that thereduction of more sterically hindered ketone A results in an opticallypure product. It should be noted that within the description hereinabsolute terms or phrases used (e.g., optically pure) are understood toinclude at least a range typically acceptable to one skilled in the art.In one example, the optically pure product referred to regarding thereduced ketone may be >90% pure. In an example, the optically pureproduct referred to regarding the reduced ketone may be >95% pure. In anexample, the optically pure product referred to regarding the reducedketone may be >99% pure. In an example, the optically pure productreferred to regarding the reduced ketone may be >99.9% pure.

In some embodiments a reduction catalyst may be a chiral catalyst. A“chiral catalyst” a defined herein is a catalyst that includes a singlestereoisomer of a chiral molecule. In one embodiment, a chiral catalystincludes a transition metal and an optically active chiral ligand.Transition metals that may be used to form a chiral catalyst forreduction of ketones include Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Re,Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, and Au. In some embodiments,a ruthenium chiral catalyst may be used to effect a stereoselectivereduction of keto-α-isopherone. The ruthenium chiral catalyst may beformed from a mixture of [RuX₂(η⁶-Ar)]₂ with an optically active amine,where X represents a halogen (e.g., F, Cl, Br, I) and Ar representsbenzene or a substituted benzene (e.g., alkyl substituted benzene). Insome embodiments, the optically active amine includes both (S)- and(R)-amino acids, and other optically active amines such as asH₂N—CHPh—CHPh—OH, H₂N—CHMe—CHPh—OH, MeHN—CHMe—CHPh—OH. Reduction ofketo-α-isopherone with a chiral catalyst may yield the optically activehydroxy ketone 116. While hydroxy ketone 116 is depicted in the (R)—form, it should be understood that the (S)— form may be formed by usingthe opposite optically active compound to form a chiral catalyst. Forexample, forming a ruthenium catalyst using (1R, 2S)-(−)-norephedrineleads to the (R)-form of the hydroxy ketone depicted below, whileforming a ruthenium catalyst using (1S, 2R)-(+)-norephedrine leads tothe (S)-form of the hydroxy ketone below. Further details regarding theuse of ruthenium catalyst for the reduction of keto-α-isopherone may befound in the paper “Synthesis of (R)- and (S)-hydroxyisophorone byruthenium-catalyzed asymmetric transfer hydrogenation of ketoisopherone”by Henning et al., Tetrahedron:Asymmetry, 11 (2000) 1849-1858, which isincorporated herein by reference.

Compound 116 may be further reduced. The remaining ketone of compound116 may be reduced to an alcohol. The resulting alcohol to which theremaining ketone of compound 116 has been reduced may be optically pure.Any type of reducing agent suitable for reducing a ketone to a hydroxygroup may be used. The reducing agent may be a chiral reducing agent oran achiral reducing agent. The stereoselectivity of the reduction athydroxyl (D) is controlled, at least in part, by the stereochemistry ofthe hydroxy group (C) as depicted in 118.

In some embodiments, a borohydride reducing agent may be used to reducethe ketone group of compound 116. In an embodiment, a hinderedborohydride reducing agent may be used to assist in achieving anenantiomerically pure reduction of the remaining ketone of compound 116.In an embodiment, the hindered borohydride reducing agent is a lithiumtrialkyl borohydride. Examples of lithium trialkyl borohydrides include,but are not limited to, lithium tri-sec-butylborohydride and lithiumtrisiamylborohydride. Reduction of the remaining ketone of 116 resultsin compound 118 having a general formula of

Other types of hindered reducing agents may be used such as hinderedaluminum hydride reducing agents may also be used to reduce ketone 116.

Alcohol D of compound 118 may be selectively protected using any numberof alcohol protecting groups known to one skilled in the art to producecompound 120 having the general structure of

where R¹ is alkyl, phenyl, aryl or silyl. In some embodiments,protecting groups may include sterically hindered protecting groups.Examples of sterically hindered protecting groups include hindered silylprotecting groups. Silyl protecting groups may include, but are notlimited to, trimethylsilane, triethylsilane, triisopropylsilane,tert-butyl dimethyl silane (i.e., TBDMS), and diphenyl-t-butylsilane. IfR¹ is a TBDMS group, the resulting protected compound has the structureof 120a

Upon protecting less sterically hindered alcohol D, more stericallyhindered alcohol C may be oxidized to a ketone. Oxidation of hydroxyl Cmay be accomplished using a variety of oxidizing reagents such aschromium oxidants, manganese oxidants, and selenium oxidants. In oneembodiment, the oxidizing agent may include, for example, pyridiniumdichromate (PDC). Oxidation of hydroxyl group C leads to opticallyactive ketone 108a, where R¹ is alkyl, phenyl, aryl or silyl.

In some embodiments, R¹ may include a protecting group (e.g., TBDMS)such that 108a has a general structure of 108b

In some embodiments, an enantiomeric excess of compound 108a may bedetermined. Enantiomeric excess may be determined by first removing anyprotecting groups, then measuring the optical purity using circulardichroism (CD) spectroscopy.

As depicted in Scheme II protected hydroxy ketone 108 may be used tosynthesize astaxanthin, as well as other carotenoid derivatives, asdescribed herein. In an embodiment, ketone 108 is reacted with anucleophilic acetylenic derivative to form an addition product 112depicted below

where R¹ is alkyl, phenyl, aryl or silyl. Compound 112 may be formed byreacting ketone 108 with a nucleophile. The nucleophile may selectivelyreact with the carbonyl group of compound 108, transforming the carbonylto an alcohol, as well as forming a new substituent at the 2 position ofthe carbonyl. In a specific embodiment compound 108 may be alkynylated.An alkyne may be reacted with compound 108 in an inert solvent (e.g.,tetrahydrofuran (“THF”)). The reaction is preferably carried out at lowtemperatures. Alkynes may include compounds having the general formulaH—C≡C—R² where R² includes:

and where R¹ is alkyl, phenyl, aryl or silyl. In some embodiments, R²may include other substituents known to one skilled in the art (e.g., H,silane substituents, alkynes, alkenes, alkyls, aryl substituents,heteroaryl substituents).Addition of alkyne H—C≡C—R² to ketone may be accomplished by forming ametal anion of the acetylene, to form the reactive nucleophilicacetylenic compound M⁺ ⁻C≡C—R², where M⁺ may be, but is not limited to,Li, Na, MgBr, Cd, or Zn. A lithium salt of alkyne H—C≡C—R² may be formedby reacting the alkyne with, for example, BuLi. Other metal salts ofalkynes may be made using methods known to one or ordinary skill in theart. The nucleophilic acetylenic compound M⁺ ⁻C≡C—R² may be reacted withketone 108 to form a coupling product 112 as depicted below:

where R² includes:

and where R¹s alkyl, phenyl, aryl or silyl.

Compound 112 may be subjected to rearrangement conditions and oxidizedto be converted into unsaturated ketone 114, as depicted below.

where R² includes:

and where R¹ is alkyl, phenyl, aryl or silyl. Unsaturated ketone 114 maybe formed by a two step process or in a novel one step rearrangementoxidation. In one embodiment, compound 112 is subjected to rearrangementconditions (e.g., treatment with aqueous acid) to effect rearrangementof the alcohol to an allylic alcohol (not shown). Subsequent oxidationof the allylic alcohol leads to the unsaturated ketone 114. This twostep procedure reduces the efficiency of the process.

In an alternate embodiment, treatment of compound 112 with an oxidantaffords the unsaturated ketone 114. This ketone is formed bysimultaneous rearrangement and oxidation of the alcohol. The oxidizingagent used in a one-step process may include, for example, chromiumoxidant (e.g., pyridinium dichlorochromate (PDC)), selenium oxidant, ormanganese oxidant.

Unsaturated ketone 114 may be reduced to olefin 104 as depicted below.

Compound 114 may be used to synthesize compound 104. Treatment ofcompound 114 with an appropriate reducing agent may reduce the alkynesubstituent to give an E-olefin as depicted above. Reducing metalreductions are particularly suited for forming E-olefins from alkynes.Reducing metal reductions may be accomplished using reagents such asLi/NH₃, Na/NH₃ and Zn/acid. In some embodiments, zinc and an acid may beused to reduce the alkyne to an alkene. The acid may include, forexample, glacial acetic acid, ammonium acetate and/or ammonium chloride.The reduction yields the E-isomer predominantly. In some embodiments,one or more protecting groups (e.g., alcohol protecting groups (R¹)) maybe removed before partially reducing the alkyne to an alkene.

Upon formation of conjugated alkene 104, the intermediate may beconverted into compound 102 having a functional group capable ofreacting with an aldehyde to form a double bond.

Examples of functionalities that may be reacted with an aldehyde includePR⁴ ₃, SO₂R⁴, or M⁺ where R⁴ is alkyl, phenyl, or aryl and M is Li, Na,or MgBr. Coupling of two “head units” with a C₁₀-aldehyde yields acarotenoid. Coupling may be accomplished using a Wittig coupling (R³ isPR⁴ ₃), sulphone coupling (R³ is SO₂R⁴), or condensation reaction (R³ isM⁺). A phosphonium salt may be synthesized from compound 104. Phosphinesand acid may be used to synthesize the phosphonium salt. Phosphines mayhave the general structure —PR⁵ ₃ or —CH₂—P(═O)(OR⁵)₂ where R⁵ is alkyl,phenyl, or aryl. Acids may include any of a number of acids known to oneskilled in the art. One example of an acid which may be used is hydrogenbromide (“HBr”).

Compound 102 may be reacted with a molecule containing an aldehydefunctionality. The functional group (e.g., the phosphonium salt) mayreact with an aldehyde functionality under appropriate conditions tocouple compound 102 to the dialdehyde. Compound 102 may be reacted witha dialdehyde in order to perform a double coupling as depicted below.

As shown above, the above-described sequence for the formation ofastaxanthin may be accomplished in a stereoselective manner to give asingle desired stereochemistry. While depicted as a stereoselectivesynthesis, it should be understood that the above described synthesizeof astaxanthin may also be accomplished without control of thestereochemistry to give a statistical distribution of stereoisomers. Insome embodiments, a method may include analyzing the distribution ofstereoisomers of a carotenoid (e.g., astaxanthin). A method allowinganalysis of the distribution of possible stereoisomers of a carotenoidmay be used to determine the outcome of a synthetic method for preparinga carotenoid. The method may also be useful for checking the purity ofcarotenoid materials provided by chemical manufacturers. In oneembodiment, a chiral HPLC column may be used to determine thestereoisomeric distribution of a carotenoid.

In an alternate embodiment, coupling of the headpiece unit with acoupling agent may be accomplished by forming pendant aldehyde groups onthe headpiece and reacting them with a coupling agent as depicted below.In some embodiments, a carotenoid, may be synthesized by condensing acompound of the general formula

with a compound of the general formula

Condensation reactions using compounds such as those pictured above may,in some embodiments, be coupled under what are commonly known as Wittigcondensation conditions. For example, the condensation may be carriedout in the presence of an alkali metal alcoholate (e.g., sodiummethylate, lithium carbonate, or sodium carbonate). The condensation maybe carried out in the presence of an alkyl substituted alkylene oxide(e.g., ethylene oxide, 1,2-butylene oxide). Appropriate solvents may beused, such as alkanols (e.g., methanol, ethanol, isopropanol). Thecondensation may be carried out over a range of temperatures. In someembodiments, the condensation may be carried out below room temperature(e.g., 0° C.).

In one embodiment, intermediates used to synthesize astaxanthin may alsobe used to synthesize other carotenoids such as lutein and zeaxanthin.For example, lutein may be synthesized using the scheme depicted below:

The synthesis of the intermediate 102 has been described before withrespect to the synthesis of astaxanthin. Synthesis of the protecteddialdehyde compound 130 and the unconjugated headpiece unit 140, havebeen described in literature procedures. The use of the syntheticmethodologies described herein to obtain headpiece 102 may increase theefficiency and/or yield of the above-described synthesis of lutein.

In another embodiment, intermediates used to synthesize astaxanthin mayalso be used to synthesize other carotenoids such as zeaxanthin. Forexample, zeaxanthin may be synthesized using the scheme depicted below:

The synthesis of the intermediate 150 is based on a modified synthesisof the intermediate 102 used to make astaxanthin. As shown above, thefinal coupling of intermediate 150 with a dialdehyde yields zeaxanthinin an analogous manner to astaxanthin. Synthesis of intermediate 150 maybe accomplished using the scheme depicted below.

In some embodiments, synthesis of the intermediate 150 may beaccomplished using the same synthetic techniques as have been describedabove for astaxanthin to obtain intermediate 120. Intermediate 120 maybe converted into saturated ketone 160 using a procedure that ismodified from the process used in the synthesis of astaxanthin. In anembodiment, a saturated ketone 160 may be formed by a two step procedureby oxidizing the hydroxyl group and reducing the double bond.Alternatively, the reduction of the double bond may be performed priorto oxidation of the hydroxyl group. The scheme for converting compound120 to 150 is shown below.

Upon protecting the less sterically hindered alcohol, the moresterically hindered alcohol of compound 120 may be oxidized to a ketone.Oxidation of the hydroxyl group may be accomplished using a variety ofoxidizing reagents such as chromium oxidants, manganese oxidants, andselenium oxidants. In one embodiment, the oxidizing agent may include,for example, pyridinium dichromate (PDC). Oxidation of the hydroxylgroup leads to an optically active ketone 108a, where R¹ is alkyl,phenyl, aryl or silyl. Hydrogenation of the double bond using catalytichydrogenation (e.g., Raney Ni, Pd/H₂, etc.) gives the intermediate 150.In other embodiments, hydrogenation may be performed to reduce thedouble bond followed by oxidation of the hydroxyl group to the ketone toform intermediate 150.

Synthesis of zeaxanthin, as shown in the above-described scheme, thenproceeds in an analogous manner to the synthesis of astaxanthin.

In an alternate method, intermediate 102 used to make astaxanthin, maybe formed using an alternate method. An alternate method for makingintermediate 120 is depicted below:

The method includes an initial step of oxidizing ketoisopherone tohydroxylated ketoisopherone as depicted below:

Suitable oxidants include chromium oxidants, manganese oxidants andperoxide oxidants. For example, in some embodiments, a cyclohexenederivative may be hydroxylated using hydrogen peroxide. After thecompound has been oxidized, the hydroxylated product is reduced to forma dihydroxylated compound having the general structure

The method may also include protecting the dihydroxylated compound. Insome embodiments, a dihydroxylate may be protected by reacting thedihydroxylated compound with a ketone (e.g., acetone). A ketone may bereacted with the dihydroxylated compound to form a protecteddihydroxylated compound having the general structure

In some embodiments, R¹ may be alkyl (e.g., methyl), aryl or each R¹together forms a cyclic ring. The method may include coupling an alkyneto the protected dihydroxylate to form an intermediate coupled product.In some embodiments, the intermediate coupled product may not beisolated. Instead the intermediate product may be directly subjected tothe next reduction process to give a product having the structure:

The intermediate coupled product may be transformed into a phosphoniumsalt product. In some embodiments, R⁵ may be alkyl or aryl.

In some embodiments, a method may include transforming a hydroxylatedproduct into a phosphonium salt product. Transforming the hydroxylatedproduct into a phosphonium salt product may include reducing thehydroxylated product to form a dihydroxylated compound having thegeneral structure

In some embodiments, the hydroxylated compound may be reducedstereoselectively.

The term “stereoselective reduction” may be generally defined asstereochemical reduction by which one of a pair of enantiomers, eachhaving at least one asymmetric carbon atom, is produced selectively,i.e., in an amount larger than that of the other enantiomer. Thestereo-differentiating reduction is classified into enantioface- anddiastereo-differentiating reductions, by which optical isomers havingone asymmetric carbon atom and those having two asymmetric carbon atomsare produced, respectively. The present reduction may be said to pertainto stereo-differentiating hydrogenation of carbonyl compounds.

In some embodiments, a carbonyl may be stereoselectively reduced suchthat the resulting chiral center comprises a stereochemistry of R or Scomprising a stereoselectivity of greater than 50%. A stereoselectivityof a reduction may be greater than 75%. A stereoselectivity of areduction may be greater than 90%. A stereoselectivity of a reductionmay be greater than 95%. A stereoselectivity of a reduction may begreater than 99%.

A stereoselective reduction of a first carbonyl of ketoisophorone (KIP)may proceed as depicted:

In some embodiments, compound 108c (S-phorenol) may be a usefulintermediate for the synthesis of certain carotenoids (e.g., zeaxanthinor astaxanthin).

Direct asymmetric reduction of KIP to 108c may save several stepsrelative to syntheses previously reported. Use of catalytic reagents forstereoselective reduction avoids expensive reagents used instoichiometric amounts for reduction. Compound 108c may be useful forsynthesis of carotenoids such as astaxanthin via derivative 108b.

KIP is known and commercially available and therefore a prime candidatefor beginning a synthesis of some carotenoids with.

Reduction of ketoisophorone can occur at C-1 and/or C-4 and/or at thedouble bond, thus problems of regioselectivity and stereoselectivitymust be solved.

1,2-reduction at C-4 has been achieved with a stoichiometric amount ofthe reagents sodium borohydride/cerium chloride (JOC, 1986, 491,incorporated herein by reference) to give racemic product. 1,2-reductionat C-4 has been achieved with 2-propanol in the presence of zirconiumoxide catalyst to give racemic product (Bull Chem Soc Jap, 1988, 3283,incorporated herein by reference).

Compound 108c has been obtained by bioprocesses. Typical are productmixtures from non-selective reduction and over-reduction. See forexample Agr Biol Chem, 1988, 2929 with Aspergillus niger, incorporatedherein by reference, the product was the undesired 4 R enantiomer. 108chas been obtained in up to 99% enantiomeric excess by esterasehydrolysis of the racemic chloroacetate ester. The maximum yieldreported was 30%. The maximum theoretical yield is 50% (Tetr Assy. 1999,3811, incorporated herein by reference). 108c has been obtained inhomochiral form by asymmetric catalytic reduction of the enol acetate ofKIP (U.S. Pat. No. 5,543,559 to Broger et al., incorporated herein byreference). This requires preparation of the enol acetate and hydrolysisof the product acetate to obtain 108c.

Direct asymmetric catalytic reduction of KIP has been reported usingchirally modified ruthenium catalysts to obtain 108c in low selectivityand maximum 76% ee (Tetr Assy, 2000, 1849, incorporated herein byreference).

There are many methods known to one skilled in the art forstereoselectively reducing a carbonyl group. Stereoselective reductionsmay be carried out using catalytic reagents (e.g., chemical,biological). Biological catalysts may include for example livingorganisms (e.g., yeast) capable of facilitating a reduction of acarbonyl. Catalytic reagents may be used due to their efficiency.Efficiency may be related to more than just a yield of a reaction orturnover, but also may include cost of the reagent as well as total costof running the reaction (e.g., cost of catalyst, mole percentage ofcatalyst required, ease of reclaiming catalyst). Catalysts may be moreattractive as possible reducing agents on an industrial scale due to areduction in related expenses.

In some embodiments, direct stereoselective reduction of KIP (includingderivatives and analogs of KIP) to the alcohol product (includingprotected alcohols, such as ethers) may include the use of reagents suchas boranes. Boranes may include at least one B-H bond (e.g., diborane,borane-THF complex, borane-methyl sulfide complex, phenoxyboranes (suchas catechol borane), amine-borane complexes, or alkoxyboranes).

In some embodiments, borane reagents may include chiral substituents.Chiral catalysts may include chiral derivatives which form weakcomplexes with the borane reductant. Chiral catalysts which form weakcomplexes with borane reductants may include amine derivatives.

In some embodiments, chiral oxazaborolidine catalysts with borane-THFmay be used to stereoselectively reduce KIP and its analogs andderivatives (as described by Prof E J Corey in U.S. Pat. No. 4,943,635and reviewed in Angew Chem Intl Engl, 1998, 37, 1986, both of which areincorporated herein by reference). In some embodiments, oxazaborolidinecatalysts may include a compound having a general structure

Using oxazaborolidine catalyst 202 with borane-THF as reductant,complete conversion may be achieved with 100% regioselectivity ofreduction of the carbonyl at C-4 and a minimum of 25% enantiomericexcess.

Enantiomeric excesses of over 55% may be achieved using compound 202. Insome embodiments, regioselectivity and enatiomeric excess may vary withtemperature, the B—H source, and/or the structure of the catalyst.

Enantiomeric excesses may be improved with purification techniques knownto one skilled in the art. In some embodiments, a chiral product may bepurified via crystallization. Compound 108c is a crystalline solidwhereas the racemate is typically obtained as non-crystalline. Thereforecrystallization of product to chiral purity may be a useful means ofachieving this end.

A stereoselective reduction of a first carbonyl of substitutedketoisophorone (KIP) may proceed as depicted:

R³ may be SiR⁵ ₃, H, alkyl, or aryl. Compound I (R³═H) is a knownsubstance, found naturally and prepared synthetically. The only otherknown example of structure 204 is the methyl ether (R³═CH₃) which wasprepared as an analytical derivative for characterization of naturalproduct 204 (R═H).

206 (R³═H) and 208 are known substances (racemic and enantiomers) anddemonstrated useful intermediates for the synthesis of racemic orhomochiral astaxanthins (Helv Chim Acta, 1981, 240, 2447, 2463,incorporated by reference herein). Derivatives and analogs of 206 (R³═H)and 208 provide useful intermediates for the synthesis of racemic orhomochiral carotenoids, as well as, other natural products and theirderivatives and analogs.

Preparation of 1 (R³═H) from ketoisophorone was described in Helv ChimActa, 1981, 2436, which is incorporated herein by reference. Reductionof 204 to racemic 206 (R³═H) using zinc in acid or hydrogen and Raneynickel and subsequent conversion to racemic 208 are also describedtherein. Preparation of the pure enantiomers of 206 (R³═H) by resolutionof racemic 206 (R³═H) via diastereomeric alpha-phenylamine salts aredescribed therein.

Desirable is direct asymmetric reduction of 204 to 206 and conversion tohomochiral 208 for use in the synthesis of homochiral carotenoids (e.g.,astaxanthin). This sequence avoids the need for problematic oxidationsteps which are required when the 3-hydroxy or 3-alkoxy substituents areabsent. The presence of a C-3 substituent may facilitate the asymmetricreduction of the carbonyl at C-4.

The only prior asymmetric reduction of 204 reported is a bioreduction of204 (R³═H) reported to give the 4S isomer of 206a (R³═H) in 65%enantiomeric excess (Helv Chim Acta, 1981, 240, 2447, incorporated byreference herein).

In some embodiments, a method may include preparation ofepoxyketoisophorone from ketoisophorone.

An epoxide of ketoisophorone may be prepared using reagents including,but not limited to, peroxides (e.g., hydrogen peroxide). There are manyepoxidation reactions known to one skilled in the art, many of whichinclude peroxides (e.g., m-ClC₆H₄CO₃H). There are other epoxidationreagents described in references such as “Comprehensive OrganicTransformations: A Guide to Functional Group Preparations” Larock, R. C.VCH Publishers, Inc. pages 456-461, which is incorporated herein byreference.

In some embodiments, a method may include preparation of3-hydroxyketoisophorone from epoxyketoisophorone.

A hydroxide anion (e.g., sodium hydroxide), followed by acidification ofthe solution may be employed to convert the epoxide to the hydroxide.

In some embodiments, a method may include preparation of3-methoxyketoisophorone from 3-hydroxyketoisophorone.

A base (e.g., sodium hydroxide, sodium carbonate) may be used todeprotonate the hydroxide in a solvent (e.g., dimethyl formamide,methanol). A methylating reagent (e.g., dimethylsulfate) may then beadded to the oxide anion in order to prepare the methoxy substituent.The methyl group may act as a protecting group masking the hydroxy groupfrom reagents used in later transformations. There are many protectinggroups for hydroxy groups known to one skilled in the art (e.g., silylprotecting groups).

In other embodiments, the hydroxy substituent of 3-hydroxyketoisophoronemay be methylated using diazomethane. Other alkylation methods mayinclude going through an intermediate (e.g., a mesylate) which issubsequently subtituted with a methoxy substitutent. An alkylation(e.g., methylation) may also be accomplished by using a methylatingagent such as trimethyl orthoformate and an acid (e.g., trifluoroaceticacid) in a solvent (e.g., methanol).

In some embodiments, the alkylation step may be circumvented by openingthe epoxy group of, for example, epoxyketoisophorone with a methoxidesalt (e.g., sodium methoxide) along with simultaneous dehydration.

In some embodiments, a method may include preparation of4-(S)-hydroxy-ketoisophorone from 3-methoxyketoisophorone.

A hydrogen source (e.g., H₂) may be used to reduce a carbonyl to ahydroxide group. A catalyst may be used to catalyze the reduction. Insome embodiments, an enantiomeric excess of a particular enantiomer maybe achieved without the use of stereoselective reagents. In someembodiments, stereoselective reagents (e.g., chiral catalysts) may beused to produce a specific enantiomer. In some embodiments, reagentswhich are not typically stereoselective reagents may be used to reduce acarbonyl to a hydroxy group. The reaction may not be stereoselective.The reaction may be stereoselective, but may be stereoselective due tothe inherent nature of the molecule. For example sodium borohydride maybe used to reduce the carbonyl to the hydroxy compound.

In some embodiments, a method may include preparation of4-hydroyxketoisophorone acetone ketal from 4-(S)-hydroxy-ketoisophorone.

A diol may be converted to an acetal using a ketone (e.g., acetone) andan acid (e.g., p-toluenesulfonic acid hydrate). The acetal group may actas a protecting group masking the diol from reagents used in latertransformations. There are other protecting groups for diols known toone skilled in the art. In some embodiments, one or more of thesynthetic steps of a method for preparing 4-hydroyxketoisophoroneacetone ketal may be combined into a “one-pot reaction” and/or anintermediate may not be isolated and/or purified before exposing it toanother set of reagents.

In some embodiments, a method may include stereoselectively reducing acarybonyl 1 of a compound 210 having the general structure

to form a chiral center 2 of a compound 212 having the general structure

R¹ may be H or OR³. R³ may be SiR⁵ ₃, H, alkyl, or aryl. R⁵ may be H,alkyl, or aryl.

In some embodiments, R³ and/or R⁵ of compound 1 may include alkyl,substituted alkyl, aryl. Alkyl may include alkyl substituents, wherealkyl comprises two or more carbons. Compound 1, where R³═H (or saltsthereof) and R³=alkyl, heteroalkyl, aryl, heteroaryl, aralkyl, orheteroaralkyl, are useful substrates for asymmetric reduction forpreparation of isomers of compound 2. R³ may include other substituentsnot listed known to one skilled in the art, even substituents typicallyunstable during reductive conditions may be used if protected properlyusing known functional protection methodology.

In some embodiments, salts formed from compound I (R³═H) may includemetals of period I or II or transition metals compatible with thereductants, ammonia, or amines (e.g., alkyl, substituted alkyl, aryl,heteroaryl, primary, secondary, or tertiary), or phosphines (e.g.,alkyl, substituted alkyl, aryl, heteroaryl, primary, secondary, ortertiary). Salts formed from compound 1 (R³═H) may contain chirality intheir structures or as associated ligands.

In some embodiments of ethers of compound 1, R³ may be any alkyl, aryl,heteroaryl, aralkyl, or heteroaralkyl group compatible with thereduction conditions. Any of the R groups may contain chiral centers orassociated chiral ligands. In certain embodiments, R³ may be an alkylgroup comprising from one to eight carbons.

A reductant may be selected from among the classes of: hydrogen, anon-gaseous hydrogen source (e.g., reduction with an alcohol, formicacid, etc.), a nucleophilic metal hydride (e.g., NaBH4 etc.), a covalentmetal hydride (e.g., Dibal), a non-metal hydride (e.g., boranes orsilanes) or metal catalyzed transfer of hydride from alcohols (e.g.,Meerwein-Pondorf-Verley reduction). The reductant may be chiral. Incertain embodiments, reductants, may include hydrogen, formic acid,isopropanol, or sec-butanol.

Catalysts for hydrogenation or transfer hydrogenation may be chosen fromamong transition metals or metal ions (e.g., such as nickel, cobalt,platinum, palladium, iridium, rhodium, and ruthenium, modified withchiral ligands or surface modifiers) capable of facilitating reductionof ketones selectively over reduction of other moieties (e.g., esters).In certain embodiments, catalysts for hydrogenation or transferhydrogenation may be complexes of rhodium (I) or Ruthenium (II) withC₂-symmetric ligands or platinum metal modified with chiral cinchonaalkaloids. Examples of ligands are known to one skilled in the art.

At least some of the intermediates 2 (R³=alkyl, etc.) are found to becrystalline. It is a desirable feature that the chiral purity ofcompound 2 may be upgraded by recrystallization.

It has been previously reported that compound 2 (R³═H) may be convertedto 3 by treatment with acetone or acetone ketals in the presence of acidcatalysts in either the racemic or chiral series. It is reported herethat compound 2 (R³=alkyl, etc.) may be converted to compound 2 (R³═H)under acidic hydrolytic conditions. It was surprisingly found thatcompound 2 (R³=alkyl, etc.) may be converted to compound 3 when treatedwith acetone in the presence of acidic catalyst.

Compound 1 may be prepared from commercially available ketoisophorone byseveral means:

-   -   1. alkylation of 1 (R³═H) with alkyl halides or sulfates in the        presence of base and solvent as appropriate. Preferred is        dimethylsulfate with sodium hydroxide in water, in the optional        presence of methanol;    -   2. treatment of 1 (R³═H) with alcohols or phenols in the        presence of an acid catalyst under conditions for physical        removal of water (e.g., distillation or azeotropic distillation)        or chemical removal of water (e.g., presence of a ketal or        orthoester); and    -   3. epoxidation of ketoisophorone followed by treatment with        alkoxide or phenoxide.

In some embodiments, a carbonyl may be stereoselectively reduced, as forexample:

In some embodiments, R¹ may be R⁵, OSiR⁵ ₃, or OR⁵. R³ may be SiR⁵ ₃,aryl, or alkyl. Alkyl may comprise two or more carbons. R⁵ may be H,alkyl, or aryl. In some embodiments, R⁵ may be methyl. R³ may be methylor hydrogen. A carbonyl may be stereoselectively reduced as below

In some embodiments, a method for reducing a carbonyl may includeselectively reducing a first carbonyl in the presence of a secondcarbonyl. The second carbonyl may be chemically distinguishable from thefirst carbonyl. For example the first carbonyl may be electronicallydistinguishable from the second carbonyl. The second carbonyl may not bereduced using the described method for reducing the first carbonyl. Forexample the second carbonyl may be described as a vinylic ester and/orand ester. The second carbonyl may be sterically hindered. For reasonssuch as these, a first carbonyl may be regioselectively reduced.

In some embodiments a reduction catalyst may be a chiral catalyst. Inone embodiment, a chiral catalyst includes a transition metal and anoptically active chiral ligand. Transition metals that may be used toform a chiral catalyst for reduction of ketones include Ti, Zr, Hf. V,Nb, Ta, Cr, Mo, W, Mn, Re, Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag,and Au. In some embodiments, a ruthenium chiral catalyst may be used toeffect a stereoselective reduction of keto-a-isopherone. The rutheniumchiral catalyst may be formed from a mixture of [RuX₂(η⁶-Ar)]₂ with anoptically active amine, where X represents a halogen (e.g., F, Cl, Br,I) and Ar represents benzene or a substituted benzene (e.g., alkylsubstituted benzene). In some embodiments, the optically active amineincludes both (S)- and (R)-amino acids, and other optically activeamines such as as H₂N—CHPh—CHPh—OH, H₂N—CHMe—CHPh—OH, MeHN—CHMe—CHPh—OH,and TsNH—CHPh—CHPh—NH₂.

In some embodiments, a chiral catalyst may include a catalyst having thestructure

In some embodiments, a method may include a stereoselective reductionsuch as

In some embodiments, a solution of(1S,2S)-N-p-toluenesulfonyl-1,2-diphenylethylenediamine may be added todichloro(p-cymene)ruthenium(II)dimer. The suspension may be heated asnecessary during which time the solids may go into solution. Thereaction may be cooled to room temperature, a solution of 204b may beadded followed by KOH.

The method may include protecting the dihydroxylated compound. In someembodiments, a dihydroxylate may be protected by reacting thedihydroxylate with a ketone (e.g., acetone). A ketone may be reactedwith the dihydroxylate compound to form a protected dihydroxylatecompound having the general structure

In some embodiments, R⁵ may be alkyl (e.g., methyl) or aryl. The methodmay include coupling the protected diol to form an intermediate coupledproduct. In some embodiments, the intermediate coupled product may notbe isolated. The intermediate coupled product may include a compoundhaving the general structure

The intermediate coupled product may be transformed into a phosphoniumsalt product having the general structure

In some embodiments, a synthetic sequence may include:

In some embodiments, an alkyne may be formed via the following syntheticsequence

In some embodiments, R³ may be SiR⁵ ₃, H, alkyl, or aryl. R⁵ may bealkyl (e.g., methyl) or aryl. R³ may include a protecting group, such asthe described silyl protecting group. There are many protecting groupsknown to one skilled in the art for masking or protecting hydroxyfunctionalities. Different protecting groups may be used depending uponwhat conditions one wants to protect the hydroxy group under and/or whatconditions one desires to deprotect and “unmask” the hydroxy group. Theabove synthetic sequence may embody other types of optically activeand/or non optically active endproducts. In some embodiments, at leastsome of the synthetic steps may be carried out in a similar manner tosimilar chemical reactions as described in other synthetic schemes asdescribed herein above and/or in the Examples section.

In some embodiments, an isomer of the alkyne coupled to the protecteddiol as described above may be employed to couple to the protected diol.The isomer of the alkyne may include a compound having the generalstructure

In some embodiments, the isomer of the alkyne may be synthesized bycoupling acetylene and methyl vinyl ketone. In some embodiments, theacetylene may be added to the methyl vinyl ketone via 1,2 addition.

Due to the instability of methyl vinyl ketone other synthetic routes mybe employed to provide the desired product. In some embodiments, stablechemical equivalents of methyl vinyl ketone may be used. Stableequivalents may include 2-(beta-bromoethyl)-2-methyl-1,3-dioxolane.

In certain embodiments, carotenoids which may be synthesized usingmethods described herein may include carotenoids based on a chemicalintermediate having the general structure

The compound depicted above embraces racemic, optically activestereoisomers and optically inactive stereoisomers. In some embodiments,R³ may be OR⁵, OSiR⁵ ₃, H, alkyl, or aryl. R⁵ may be H, alkyl, or aryl.In some embodiments, R⁷ may include C—R³ or C═O. A method ofsynthesizing such a compound may include transforming a halogenatedderivative having the general structure

into a phosphorous compound having the general structure

In some embodiments, R⁵ may be alkyl or aryl. X may be a halogen (e.g.,Br, Cl). The method may include reacting the phosphorous compound withan aldehyde or an aldehyde equivalent having a general structure

to form a alcohol coupling product having the general structure

The method may include transforming the alcohol coupling product into ahalogenated coupling product having the general structure

In some embodiments, R⁵ may be alkyl or aryl. X may be a halogen (e.g.,Br, Cl).

In some embodiments, a method may include transforming the halogenatedcoupling product into a phosphonium salt product having the generalstructure

R⁵ may be alkyl or aryl. X may be a halogen (e.g., Br, Cl).

In some embodiments, a method may include reacting the phosphonium saltproduct with a dialdehyde having the general structure

to form a carotenoid chemical intermediate having the general structure

In some embodiments, R³ may be OR⁵, OSiR⁵ ₃, H, alkyl, or aryl. R⁵ maybe H, alkyl, or aryl. In some embodiments, R⁷ may include C—R³ or C═O.

In some embodiments, a carotenoid chemical intermediate may include acompound having the general structure

In some embodiments, a synthetic sequence may include:

In some embodiments, carotenoid chemical intermediates may be used tosynthesize naturally occurring carotenoids as well as carotenoid analogsand carotenoid derivatives. Carotenoid chemical intermediates may beused to synthesize naturally occurring carotenoids such as lycopene andlycophyll, and lycopene/lycophyll analogs and lycopene/lycophyllderivatives.

In some embodiments of a method to synthesize lycopene and lycophyll,and its derivatives and/or analogs, the chemical intermediate picturedabove having the general structure

may be coupled with a phosphonium salt product having the generalstructure

to form lycopene having the general structure

In some embodiments, Y may include —CH₂—PR⁵ ₃ or —CH₂—P(═O)(OR⁵)₂. R⁵may be alkyl or aryl.

In some embodiments, methodologies as described herein (e.g., methodsfor synthesizing lycopene) may be used to prepare acyclic carotenoids,as well as, derivatives and/or analogs of acyclic carotenoids. Of courseit is understood that at least some of the intermediates used tosynthesize acyclic carotenoids are also useful in the preparation ofcarotenoids containing cyclic rings (referred to herein sometimes ascyclic carotenoids, e.g., astaxanthin).

In some embodiments, a compound prepared by the method described hereinmay include an enantiomeric excess of at least one of the possiblestereoisomers of the compound.

In some embodiments, a compound prepared by the method described hereinmay include an excess of a stereoisomer relative to the stereoisomer'sstatistical abundance.

In certain embodiments, carotenoids, carotenoid derivatives, orcarotenoid analogs which may be synthesized using methods describedherein may include carotenoids based on a chemical intermediate havingthe general structure

Compound 214 may be coupled to a phosphonium salt product 216 having thegeneral structure

to form protected carotenoid 218 having the general structure

In some embodiments, Y may be PR⁵ ₃ or P(═O)(OR⁵)₂. R³ may be SiR⁵ ₃, H,alkyl, or aryl. R⁵ may be alkyl or aryl. In some embodiments, a solutionof LiOMe (e.g., in methanol) may be used to couple the two compounds toprepare the protected carotenoid.

In some of the phosphonium salt product 216 embodiments, Y may be PR⁵ ₃,R⁵ may be phenyl, and such that phosphonium salt product 216 has thegeneral structure

In some embodiments, X may be F, Cl, Br, or I. In some embodiments, R³may be methyl and X may be Br.

In some embodiments, a method may include reducing protected carotenoid218 to form carotenoid 220 having the structure

In some embodiments, R³ may be SiR⁵ ₃, H, alkyl, or aryl. R⁵ may bealkyl or aryl. In some embodiments, R³ may be H when protectedcarotenoid 218 is reduced to an alcohol forming carotenoid 2H. Reducingagents (e.g., DIBAL or Diisobutylaluminium hydride) known to one skilledin the art may be used to reduce the protected carotenoid 218 to formthe carotenoid 220. Other reducing agents known to one skilled in theart may be used.

In some embodiments, carotenoid derivatives and analogs may besynthesized from naturally occurring carotenoids. These carotenoids maybe synthetically produced and/or isolated from natural sources.

In some embodiments, a method may include condensing carotenoid 220 withsuccinic anhydride to prepare compound 222 having the general structure

222. In some embodiments, R³ may be SiR⁵ ₃, H, alkyl, or aryl. R⁵ may bealkyl or aryl. In some embodiments, R3 may include a co-antioxidant(e.g., Vitamin C, Vitamin C analogs and derivatives) and/or othersubstituents described herein. A base (e.g., N,N-diisopropylethylaminein a solvent such as CH₂Cl₂) may be used to facilitate condensation ofcarotenoid 220 to succinic anhydride. A non-nucleophilic base may beused. The method may include forming a salt 224 of compound 222 having ageneral structure

224. wherein X is a counterion. In some embodiments, X may be acounterion. X may include inorganic salts and/or organic salts. X mayinclude, but is not limited to, Li, Na, or K. NaOMe may be used toconvert the acid to the salt. Other reagents such as LiOMe, NaOEt, aswell as other based may be used to prepare the salt.

In some embodiments, a method may include phosphorylating carotenoid 220to form compound 226 having the general structure

221. In some embodiments, Y may be PR⁵ ₃ or P(═O)(OR⁵)₂. R³ may be SiR⁵₃, H, alkyl, or aryl. R⁵ may be H, alkyl, benzyl, or aryl. The methodmay include forming a salt 223 of compound 226 having a generalstructure

223. In some embodiments, X may be a counterion. X may include inorganicsalts and/or organic salts. X may include, but is not limited to, Li,Na, or K. NaOMe may be used to convert the acid to the salt. Otherreagents such as LiOMe, NaOEt, as well as other bases may be used toprepare the salt.

In some embodiment, a method may include preparing phosphonium saltproduct 216 by oxidizing ester 228 having the general structure

to form aldehyde 230 having the general structure

Selective oxidizing agents (e.g., SeO₂ in a solution of for example 95%ethanol) may be used to oxidize up to the aldehyde. The method mayinclude oxidizing aldehyde 230 to form oxidized product 232 having thegeneral structure

Selective oxidizing agents (e.g., NaClO₂, Na₂HPO₄, Me₂C═CHMe,t-BuOH/H₂O) may be used to oxidize up to the acid and/or ester. Oxidizedproduct 232 may be selectively deprotected to form product 234 havingthe general structure

Selective bases (e.g., K₂CO₃, MeOH/H₂O) may be used to convert oxidizedproduct 232 (e.g., to the alcohol and/or ether). Conversion of product232 to product 234 may be viewed as more of a deprotection of analcohol. The method may include halogenating product 234 to formhalogenated product 236 having the general structure

In an embodiment where product 234 includes an alcohol, halogenation ofalcohols may be accomplished by a variety of methods (e.g., CBr₄/Ph₃P ina polar solvent such as THF). Halogenated product 236 may be convertedto the phosphonium salt product 216. Conversion of the halogen to thephosphonium salt may include using Ph₃P in a solvent such as EtOAc. Insome embodiments, X may be a counterion. X may include inorganic saltsand/or organic salts. X may include F, Cl, Br, or I. R³ may be SiR⁵ ₃,H, alkyl, or aryl. R⁵ may be alkyl, benzyl, or aryl.

In some embodiments, a multi-gram scale total synthesis of lycophyll(16,16′-dihydroxy-lycopene; ψ,ψ-carotene-16,16′-diol) may be based on a2 (C10)+C20 synthetic methodology using the commercially availablematerials geraniol (C10) and crocetindialdehyde (C20). A late-stagedouble Wittig olefination of crocetindialdehyde may be used to form thelycophyll scaffold. The double Wittig may generate a mixture of polyenicgeometric isomers that may be separated (e.g., using HPLC). Theall-trans lycophyll may be achieved in >95% purity using about 8 linearsynthetic steps. The disuccinate and diphosphate sodium salts of therare carotenoid may then be prepared. Carotenoid derivatives and analogs(e.g., disuccinate and diphosphate sodium salts) may be readilydispersible in water without need for heat, detergents, co-solvents, orother additives. Retrometabolic in design, these novel derivatives couldfind utility in those applications where parenteral delivery oftherapeutically relevant forms of lycophyll are desired.

Studies in cultured human cells have shown that lycopene 2F, the primarycarotenoid in tomatoes, can be growth inhibitory against transformedcells as well as normal prostatic epithelium, alone and/or incombination with other antioxidants (e.g. vitamin E). In animal studies,the results regarding protection against proliferation of transformedcells induced with various carcinogenic agents have been positive. Forexample, in the ferret, the most representative model in terms ofabsorption-distribution-metabolism-excretion (ADME) for humans, lycopenewas in fact protective against cigarette-smoke induced lung pathology.Epidemiological studies in humans clearly support an association betweendietary consumption of lycopene-containing food products and a lowerrisk of prostate cancer. These lycopene-containing food products alsocontain lycophyll, albeit in lower relative amounts. In some cases, thenatural dietary mixture of carotenoid compounds has efficacy in thesesettings, and synthetically-prepared or naturally-isolated lycopene doesnot. In some embodiments, a method of treating disease in a humansubject may include administering to the human subject a pharmaceuticalor nutraceutical composition including a predetermined ratio of two ormore geometric and/or stereoisomers of a structural analog or derivativeor synthetic intermediate of a carotenoid. In some embodiments, a methodof treating disease in a human subject may include administering to thehuman subject a pharmaceutical or nutraceutical composition including apredetermined ratio of two or more structural analogs or derivatives orsynthetic intermediates of a carotenoid. Prospective, randomizedclinical trials in humans also demonstrate improved indices ofproliferation and oxidative stress across a range of oral doses incancer patients. Delivery of a highly potent radical scavenger toprostatic tissue may restore or augment endogenous antioxidant levels.

Lycoxanthin 2G and lycophyll 2H, which can be isolated from the red,ripe berries of Solanum dulcamara, as well as tomatoes and watermelon,are C40 lycopene-like xanthophylls functionalized with primary hydroxylgroups. The originally proposed chemical structures of the xanthophyllshowever lacked complete assignment and required further studies thatwere realized in the early 1970's. Utilizing high-resolution massspectroscopy and NMR, the regiochemistry of the hydroxyl groups wascharacterized. Unambiguous confirmation of both structures were obtainedapproximately one year later, facilitated by the total syntheses oflycoxanthin and lycophyll reported by Kjøsen and Liaaen-Jensen in 1972.The original total synthesis was based on a C10+C20+C10 syntheticparadigm, in part due to the commercial availability of C20 dialdehyde(crocetindialdehyde). Up to the present, little additional chemical orbiological information has accumulated in the primary literature foreither compound.

Lycophyll was prepared by total synthesis at multiple gram scale for thecurrent testing and derivatization to novel water-soluble,water-dispersible compounds. Isolation from natural sources demonstrateshigh cost, significant manpower, and generally low yields.Retrosynthetic analysis of the target xanthophyll revealed an efficientmethodology utilizing at least some commercially available materials. Incases where commercial material was not available, these intermediateswere synthesized in appropriate amounts. In some embodiments,commercially available materials may include geranyl acetate, aprotected form of geraniol (C10), and/or crocetindialdehyde (C20). Amethod may include a total synthesis of acyclic carotenoids (e.g.,lycophyll). In some embodiments, a synthesis of, for example, lycophyllmay be realized in about 8 synthetic steps (Schemes 1 and 2). Syntheticsteps may include an “endgame” double-Wittig olefination thatsuccessfully forms the target C40 scaffold while generating a mixture ofgeometric isomers (Scheme 2). The isomeric mixture may be deconvolutedto yield the target all-trans lycophyll. Deconvolution may include, butis not limited to, thermal or liquid chromatographic methods. Themethodology shown in Schemes 1 and 2 for synthesizing lycophyll may beused to synthesize other acyclic carotenoids, carotenoid derivatives,and carotenoid analogs.

Research has shown that targeted derivatization of carotenoids cansuccessfully increase the aqueous solubility and/or dispersibility ofthe highly lipophilic natural scaffolds. These compounds havedemonstrated beneficial effects as direct aqueous radical scavengers, asmyocardial salvage agents in experimental infarction models, as agentsameliorating and/or preventing chronic liver injury, and/or as cancerchemopreventive agents. The derivatives have shown increased utility asparenteral agents in these settings, as well as improved oralbioavailability in model animal studies. Currently, our efforts haveextended along these lines to include the derivatization of the rarexanthophyll lycophyll, specifically directed by principles ofretrometabolic drug design. Acquisition of lycophyll through totalsynthesis (Scheme 1 and 2) facilitated the generation ofwater-dispersible lycophyll succinic and phosphoric diester salts(Scheme 3). These novel compounds are readily dispersible in waterwithout need of heat, detergents, co-solvents, or other additives. Suchderivatives will likely find application in those indications in whichparenteral delivery of highly-potent radical scavengers possessing thelycopene scaffold are necessary to achieve their intended purpose.Specifically, these compounds will be evaluated for efficacy incontemporary in vitro and in vivo cancer chemoprevention models,utilizing the natural tissue tropism of these compounds in mammals.

In some embodiments of a method to synthesize lycopene and itsderivatives and/or analogs, a phosphonium salt product having thegeneral structure

may be coupled with an aldehyde product having the general structure

to form lycopene having the general structure

In some embodiments, Y may include —CH₂—PR⁵ ₃ or —CH₂—P(═O)(OR⁵)₂. R⁵may be alkyl or aryl.

In some embodiments, a lycopene analog or a lycopene derivative mayinclude one or more substituents. At least one of the substituents mayinclude hydrophilic substituents. In some embodiments, substituents mayinclude chemically reactive substituents which serve as chemicalintermediates.

In some embodiments, carotenoid chemical intermediates may be used tosynthesize naturally occurring carotenoids such as xanthophylls. Amethod may include coupling a phosphonium salt product having thegeneral structure

with a dialdehyde having the general structure

to form a carotenoid having the general structure

In some embodiments, R¹ and R² may be H or OR³. R³ may be SiR⁵ ₃, H,alkyl, or aryl. R⁵ may be alkyl or aryl. Y may include —CH₂—PR⁵ ₃ or—CH₂—P(═O)(OR⁵)₂. R⁷ may include C—OR³ or C═O. Examples of xanthophyllcarotenoids than may be synthesized using this methodology include, butare not limited to, astaxanthin, lutein, zeaxanthin, and canthaxanthin.

In some embodiments, one or more of the conversions and/or reactionsdiscussed herein may be carried out within one reaction vesselincreasing the overall efficiency of the synthesis of the final product.In some embodiments, a product of one reaction during a total synthesismay not be isolated and/or purified before continuing on with thefollowing reaction. A reaction may instead only partially be worked up.For example, solid impurities which fall out of solution during thecourse of a reaction may be filtered off and the filtrate washed withsolvent to ensure all of the resulting product is washed through andcollected. In such a case the resulting collected product still insolution may not be isolated, but may then be combined with anotherreagent and further transformed. In some cases multiple transformationsmay be carried out in a single reaction flask simply by adding reagentsone at a time without working up intermediate products. These types of“shortcuts” will improve the overall efficiency of a synthesis,especially when dealing with large scale reactions (e.g., along thelines of pilot plant scale and/or plant scale).

An example of increasing the overall efficiency of a synthesis mayinclude reducing the alkyne of compound 114 to an alkene formingcompound 104. In some embodiments, zinc and an acid may be used toreduce the alkyne to an alkene. The acid may include, for example,glacial acetic acid. The resulting zinc acetate may then be filteredoff, and the filter cake washed with an organic solvent (e.g., methylenechloride) to ensure collection of as much of the resulting productcompound 104 as possible. The resulting product compound 104, still insolution, may then be added dropwise over a period of time (e.g., 30minutes) to an aqueous solution of acid (e.g., HBr) and the resultingmixture stirred (e.g., for 10 minutes). The organic phase may beseparated from the aqueous phase and triphenylphosphine added to theorganic phase without isolating the previous product from solution. Theaddition of triphenylphosphine may result in compound 102. Dialdehydecompound 112 may be added to the resulting solution of compound 102 andcooled down (e.g., to about 0° C.). A base in solution may be added tothe solution (e.g., sodium methoxide in methanol) dropwise. Afterstirring (e.g., about 5 hours), the solution may be finally fully workedup to acquire the purified isolated compound 104.

It has been stated that the compound of formula 100 embraces racemic andoptically active and optically inactive stereoisomers. In someembodiments, a specific example of may include the synthesis ofastaxanthin having a general formula of

In an embodiment, carotenoid derivatives may be synthesized fromnaturally-occurring carotenoids. The carotenoids may include structures2A-2F depicted in FIG. 1. In some embodiments, the carotenoidderivatives may be synthesized from a naturally-occurring carotenoidincluding one or more alcohol substituents. In other embodiments, thecarotenoid derivatives may be synthesized from a derivative of anaturally-occurring carotenoid including one or more alcoholsubstituents. The synthesis may result in a single stereoisomer. Thesynthesis may result in a single geometric isomer of the carotenoidderivative. The synthesis/synthetic sequence may include any priorpurification or isolation steps carried out on the parent carotenoid.Synthesis of carotenoid derivatives can be found in U.S. PublishedPatent Application Nos. 2004-0162329 and 2005-0113372, both of which areincorporated herein by reference.

EXAMPLES

Having now described the invention, the same will be more readilyunderstood through reference to the following example(s), which areprovided by way of illustration, and are not intended to be limiting ofthe present invention.

Example 1 Preparation of (R)-4-hydroxyisophorone (R)-116

All solvents were free of O₂. And the reactions were done under N₂.Benzeneruthenium (II) dimer (19.72 g, 39.42 mmol, 0.4 mol %) and (1R,2S)-(−)-norephedrine (99%) (24.14 g, 159.67 mmol, 1.62 mol %) weredissolved in a 12 L three-necked flask containing 2-propanol (7.5 L).After stirring the red solution for 45 min at 80° C., the heat wasremoved. It was transferred to a 50 L three-necked flask containing2-propanol (28 L). 109 (1500 g, 9.86 mol) and 0.1 M potassium hydroxidein 2-propanol (3945 ml, 0.0.395 mol, 4 mol %) were added. After 3 h (TLCshowed the reaction was done), the red solution was filtered through ashort silica gel pad and the filtrate was evaporated to dryness toobtain solids (about 1600 g). After five times recrystallization from^(i)Pr₂O (500 ml×5), 912 g of (R)-116 was obtained. The yield: 60%. ¹HNMR (CDCl₃, 300 MHz): δ 1.02 (s, 3H), 1.07 (s, 3H), 1.97 (s, 1H), 2.04(t, J=1.2 Hz, 3H), 2.21 (d, J=16.3 Hz, 1H), 2.39 (d, J=16.4 Hz, 1H),4.03 (d, J=6.6 Hz, 1H), 5.86 (br s, 1H). ¹³C NMR (CDCl₃, 75 MHz): δ21.22, 21.46, 26.89, 38.48, 48.97, 76.89, 126.29, 160.81, 198.79.[α]_(D) ²³+105.34 (c=1.006, MeOH), literature [α]_(D) ²²+105.9 (c=1.00,MeOH).

Example 2 Preparation of (1R, 4S)-2,6,6-trimethyl-2-cyclohexen-1,4-diol(1R,4S)-118

To a solution of L-Selectride (5674 mL, 1 M in THF, 1.25 equiv), asolution of compound (R)-116 (700 g, 4.54 mol, 1 equiv) in THF (3000 mL)was added dropwise at −78° C. After stirring for 1.5 h, the mixture wassequentially treated with H₂O (600 mL), 4N NaOH (1450 mL). Afterextractions with AcOEt (500 ml×5) and the combined organic phase wasdried and concentrated. To the residue was charged 3000 mL of hexanes,then the mixture was filtered. The solid was washed with hexanes (200mL×3). The solid crude product was purified by flash chromatographyusing Hexanes/AcOEt (3/1) as an eluent. 645 g of compound (1R,4S)-118was obtained (yield: 91%). Recrystallized from 1000 ml of EtOAc toobtain 504 g (70%) of (1R,4S)-118. ¹H NMR (CDCl₃, 500 MHz): δ 0.86 (s,3H), 1.02(s, 3H), 1.45 (dd, J=12.8,9.5 Hz, 1H), 1.67 (ddt, J=12.8, 6.3,1.1 Hz, 1H), 1.84 (t, J=1.7 Hz, 3H), 3.34 (s, 1H), 4.18 (m, 1H), 5.54(br s, 1H). [α]_(D) ²³+68.63 (c=1.6000, CHCl₃), literature [α]_(D)²⁴+67.4 (c=0.27, CHCl₃).

Example 3 Preparation of (1R,4S)-4-tert-Butyidimethylsilyloxy-2,6,6-trimethyl-2-cyclohexen-1-ol (1R,4S)-120a

A mixture of enantiomerically pure (1R, 4S)-118 (1000 g, 6.40 mol),TBDMSCI (1194 g, 7.68 mol, 1.2 eq) and imidazole (566.37 g, 8.32 mol,1.3 eq) in DMF (9 L) was stirred at room temperature for 1 hr and 20min. Water (2 L) was added, aqueous phase was extracted with diethylether (2000 ml×3). The combined organic layer was dried over Na₂SO₄.After concentration, the crude product (1R, 4S)-120a was subjects tonext step without further purification.

Example 4 Preparation of(S)-4-tert-Butyldimethylsilyloxy-2-cyclohexenone (S)-108b

(1R, 4S)-120a (−6.40 mol) was added to a mixture of PDC (3613 g, 1.5 eq)and DMF (8000 ml), which was cooled by ice-water. And then, the mixturewas stirred for 1 h and 10 min at rt. Ether (8L) was added. The mixturewas passed through a pad of celite. Then solution was washed with water(3L×2). The organic phase was dried over Na₂SO₄. 1718.2 g of (S)-108b(Yield: 100%, two steps from 118 to 108b) was obtained after columnchromatography (hexanes/ethyl acetate, 50/1˜30/1). ¹H NMR (CDCl₃, 500MHz): δ 0.12 (s, 3H), 0.13(s, 3H), 0.92 (s, 9H), 1.11 (s, 3H), 1.14 (s,3H), 1.78 (brs, 3H), 1.87 (dd, J=12.9, 9.8 Hz, 1H), 1.99 (ddd, J=12.9,5.4, 1.8 Hz, 1H), 4.55 (m, 1H), 6.50 (br s, 1H).

Example 5 Determine the ee Value of Compound (S)-108b

To a solution of compound 108b (40 g, 112 mmol) in THF (450 ml),^(n)BU₄NF (29.22 g, 112 mmol) in 150 ml of THF was added. After 30 min,200 ml of water and 500 ml of EtOAc was added. The organic phase wasthen washed with a half-saturated brine (400 ml×2) and brine (400 mL).It was dried and concentrated and subjected to column chromatography(hexane/ethyl acetate, 5/1) to give 20.25 g of (S)-108c (92%). [α]_(D)²³−48.0 (c=1.98, EtOH), literature [α]_(D) ²⁰−46.7 (c=1.0, EtOH). Theracemic 108c was separated using a chiral HPLC column; baselineseparation was not achieved. Reverse phase HPLC column, Pirkle covalent,(S,S) Whelk-O 1, spherical silica; Eluent, 3:97 2-propanol:hexane, 1ml/min. For racemic 108c, t₁=14.07 min, t₂=14.67 min. Only one peak wasdetected for (S)-108c using the same HPLC condition T_(s)(108c)-14.74min.

Example 6 Preparation of Compounds 112a

A mixture of alkyne 110a (689.3 g, 4.10 mol, 1.1 eq) and THF (13 L) wascooled to −78° C., BuLi (1640 mL, 2.5 M, 4.10 mL, 1.1 eq) was addeddropwise. After 2 h, compound (S)-108b (1000 g, 3.725 mol) in 2L of THFwas added dropwise. In the 4 hrs, the temperature was allowed to raisefrom −78° C. to −25° C. NH₄Cl saturated solution (500 mL) and brine (500mL) was added and extracted with EtOAc (3000 mL×1). Dried. Afterconcentration, the crude product 112a (˜1770 g) was subjected to nextstep without further purification.

Example 7 Preparation of Compounds 114a

A solution of compounds 112a (˜3.75 mol) in DCM (2 L) was added dropwiseto a mixture of PDC (2101.86 g, 5.58 mol, 1.5 eq), NaOAc (458.16 g, 5.58mol, 1.5 eq), 4 Å MS (1000 g) and DCM (10 L). After 24 h, ethyl acetate(2000 ml) was added and it was subjected to a short silica gel pad andwashed with ethyl acetate. After concentration, the crude product 114a(1710 g) was subjects to next step without further purification. ¹H NMR(CDCl₃, 300 MHz): δ 0.44 (s, 3H), 0.13 (s, 3H), 0.87 (s, 9H), 1.12 (td,J=6.9, 2.7 Hz, ˜3H), 1.21-1.32 (m, ˜10H), 1.59 (s, ˜1.5H), 1.62 (s,˜1.5H), 1.83-2.2 (m, ˜4H), 3.32-3.70 (m, ˜2H), 4.29 (dd, J=11.1, 6.9 Hz,1H), 4.87 (q, J=5.4 Hz, 0.5H), 4.95 (q, J=5.4 Hz, ˜0.5H), 5.18 (d, J=9.9Hz, 1H), 5.49 (dd, J=17.4,9.9 Hz, 1H), 5.83 (dd, J=17.1, 10.2 Hz,˜0.5H), 5.95 (dd, J=17.1, 10.2 Hz, ˜0.5H). [α]_(D) ²⁶−106.13 (c=1.446,1,4-dioxane)

Example 8 Preparation of Compounds 114b

To a solution of compound 114a (1000 g, 2.303 mol) in 6000 mL of THF,was added 1450 ml of aq HCl (450 mL of con. HCl diluted with 1000 mL ofwater). The mixture was stirred for 4 hrs, sodium chloride (300 g) and3L of ethyl acetate were added. Organic phase was separated and washedwith water (2000 mL×1), the mix solution of saturated NaHCO₃ solution(2000 mL) and brine (200 mL). Combined aqueous phase was extracted withethyl ether (20000 mL×1). Washed with water (500 ml), brine (500 ml).Dried. 980 g of compound 114b was obtained after column chromatography(hexanes/ethyl acetate, 100/0 to 1/1). The yield was 57% (three steps,from 108b to 114b). ¹H NMR (CDCl₃, 300 MHz): δ 1.27 (s, 3H), 1.32 (s,3H), 1.64 (s, 3H), 1.77 (t, J=13.8 Hz, 1H), 1.97 (s, 3H), 2.19 (dd,J=12.9, 6.0 Hz, 1H), 2.51 (br s, 3H), 3.62 (br s, 1H), 4.31 (dd, J=13.5,5.4 Hz, 1H), 5.18 (d, J=10.2 Hz, 1H), 5.51 (brd, J=17.1 Hz, 1H), 6.02(br dd, J=17.1, 10.2 Hz, 1H).

Example 9 Preparation of Phosphonium Salt (S)-102a from Alkynediol 114b

650 g of alkynediol 114b (2.62 mol) was added to a mixture of 4300 mL ofmethylene chloride and 4300 mL of H₂O. After cooling to 0° C., NH₄Cl(280.07 g, 5.24 mol, 2 eq) and Zn (256.67 g, 3.93 mol, 1.5 eq) wasadded. Then the reaction mixture was stirred for 3.5 h at 0˜5° C. andthe reaction was checked with HPLC. The mixture was filtered through apad of celite, washed with DCM (500 ml×5). The organic phase was dried.To this solution, 387.6 mL of 48% aqueous HBr (3.4 mol, 1.3 eq) wasadded in two portions at −8° C. After 30 min, the reaction temperaturewas raised to −2° C. Water (1000 ml) was run in, and the organic phasewas separated off. The organic phase was washed with water (1000 ml×3).To the organic solution was added 23 mL of 1,2-epoxybutane. Whilecooling to −10° C., 755.3 g (2.88 mol, 1.1 eq) of triphenylphosphine wasadded. After PPh₃ was dissolved, another 23 mL of 1,2-epoxybutane wasadded and the mixture was stirred at rt for 3.5 h. Concentrated and¹BuOMe (1500 mL) was added to precipitate the phosphonium salt. Thesolids were filtered and washed with ¹BuOMe (100 ml×2). 1000 g of 102a(66%, three steps from 114b to 102a) was obtained.

Example 10 Preparation of (3S,3′S)-all-E-astaxanthin

To a mixture of phosphonium salt (S)-102a (463 g, 0.804 mol, 2.2 eq), 4AMS (100 g) and C₁₀-dialdehyde (2,7-dimethyl-2,4,6-octatrienedial 122)(60 g, 0.365 mol, 1 eq) in DCM (7 L) at 0° C., MeONa in MeOH (30 wt %,151 mL, 0.804 mol, 2.2 eq) was added dropwise. After 4 h, the additional42 g of phosphonium salt (S)-102a (42 g, 0.2 mol) and 14 mL of MeONa inMeOH (30 wt %, 0.2 mol) was added. After 21 h, the mixture was filteredthrough a silica gel pad (eluents: DCM/EtOAc ˜DCM/MeOH). Concentratedand filtered to obtain 110 g of crude product. The crude product (297 g)was mixed with 1000 ml of ethyl alcohol refluxed for 3 h. After cooling,filtered and washed with ethyl alcohol (50 ml×2) to obtain 221 g of(3S,3′S)-all-E-astaxanthin. ¹H NMR (CDCl₃, 300 MHz): δ 1.21 (s, 6H),1.32 (s, 6H), 1.81 (t, J=13.2 Hz, 2H), 1.94 (s, 6H), 1.99 (s, 6H) and2.00 (s, 6H), 2.15 (dd, J=12.6, 5.7 Hz, 2H), 4.32 (dd, J=13.8, 5.7 Hz,2H), 6.18-6.72 (m, ˜14H).

Example 11 Preparation of Compounds 110a

Ethyl vinyl ether (788 mL) was cooled to 5° C. and treated with PTSA(450 mg) followed by the slow addition of compound 110b (freshlydistilled, 450 g, 4.68 mol). After the addition was done, the reactionmixture was kept at rt for 3 h, quenched with triethylamine (3 mL), andthen distilled to yield acetal 110a (770 g, 97.8%). Bp: ˜80° C./20 mmHg.

Example 12 Preparation of 2-(Triphenyl-phosphanylidene)-propionic acidethyl ester

Raw Materials FW Quantity Used Moles Ethyl 2-bromopropionate 181.03  1.0Kg 5.52 mol Triphenyl Phosphine 262.29  1.6 Kg 6.10 mol PotassiumCarbonate 138.21 800 g 5.79 mol EtOAc 10 L MeOH 10 L

1.6 Kg (6.10 mol) triphenyl phosphine was dissolved in 10 L ethylacetate and 1.0 Kg of ethyl 2-bromopropionate was added into the abovesolution. The reaction mixture was stirred at room temperature for 2days. White solid was filtered off and the precipitate was washed withethyl acetate. The resulting compound was dissolved in methanol andtreated with saturated aqueous potassium carbonate. After stirring for 2h, the yellow solid was filtered off and washed with water to give 1.5Kg (75%) of desired product.

Example 13 Preparation of 4-Hydroxy-2-methyl-but-2-enoic acid ethylester

Raw Materials FW Quantity Used Moles 2-(Triphenyl- 362.40 886 g 2.44 molphosphanylidene)- propionic acid ethyl ester Glycoaldehyde dimer 120.10140 g 1.17 mol DCM 10 L

886 g (2.44 mol) of 2-(triphenyl-phosphanylidene)-propionic acid ethylester in methylene chloride (4 L) was added dropwise into a refluxingsolution of glycoaldehyde dimer (140 g, 1.17 mol) in methylene chloride(6 L). After refluxing for 4 h, the solvent was evaporated. Resultingcrude product was fractionated (bp 108-114° C. at 2 mmHg) to give 304 g(90%) pure product as an oil. ¹H-NMR (300 Hz CDCl₃) δ 6.88 (t, 1H, CH),4.35 (d, 2H, CH₂OH), 4.20 (q, 2H, OCH₂), 1.85 (s, 3H, CH₃), 1.30 (t, 3H,CH₃).

Note: This process was repeated and 660 g title compound was collected.

Example 14 Preparation of 4-Bromo-2-methyl-but-2-enoic acid ethyl ester

Raw Materials FW Quantity Used Moles 4-Hydroxy-2-methyl-but-2-enoic144.17  567 g 3.93 mol acid ethyl ester Carbon tetrabromide 331.63 1.44kg 4.34 mol Triphenyl phosphine 262.29 1.13 kg 4.30 mol THF 8 L

To a cooled solution (0° C.) of 4-hydroxy-2-methyl-but-2-enoic acidethyl ester (567 g, 3.93 mol) in THF (8 L) was added carbon tetrabromidefollowed by triphenyl phosphine. The reaction mixture was slowly warmedto room temperature and stirred overnight. White solid (identified ascompound 6) was isolated by filtering. The filtration was condensed andadded ether, the resulting white precipitated (identified as triphenylphosphate and triphenyl phosphine) was filtered off and discarded. Etherwas evaporated and the resulting crude product was used without furtherpurification in the next step.

Note: This process was repeated until 660 g of4-hydroxy-2-methyl-but-2-enoic acid ethyl ester was consumed.

Example 15 Preparation of 2-Methyl-4-(triphenyl-phosphanyl)-but-2-enoicacid ethyl ester bromide salt

Raw Materials FW Quantity Used Moles 4-Hydroxy-2-methyl-but-2-enoic207.07  940 g 4.54 mol acid ethyl ester Triphenyl phosphine 262.29 1.34Kg 5.11 mol EtOAc 10 L

940 g (4.54 mol) of 4-hydroxy-2-methyl-but-2-enoic acid ethyl ester wasadded into the solution of triphenyl phosphine (1.34 Kg, 5.11 mol) in 10L ethyl acetate. The reaction mixture was stirred at room temperaturefor 2 days. The resulting white precipitate was filtered and washed withethyl acetate to give 2.11 kg (99%) of the title compound. ¹H-NMR (300Hz DMSO-d₆) δ 7.78-7.95 (m, 15H, ArH), 6.40 (q, 1H, CH), 4.76 (q, 2H,CH₂P), 4.10 (q, 2H, CH₂), 1.60 (d, 3H, CH₃), 1.15 (t, 3H, CH₃).

Note: This process was repeated and 4.2 Kg title compound was collected

Example 16 Preparation of2,6,11,15-Tetramethyl-hexadeca-2,4,6,8,10,12,14-heptaenedioic aciddiethyl ester

Raw Materials FW Quantity Used Moles2-Methyl-4-(triphenyl-phosphanyl)-but-2-enoic acid ethyl ester bromidesalt 469.35 2006.6 g 4.28 mol 2,7-Dimethyl-octa-2,4,6-trienedial 164.20  234 g 1.43 mol NaOMe/MeOH (30%)  54.02   749 mL 4.00 mol Methylenechloride 5 L

To a refluxing solution of 2-Methyl-4-(triphenyl-phosphanyl)-but-2-enoicacid ethyl ester bromide salt (2006.6 g, 4.28 mol) and2,7-Dimethyl-octa-2,4,6-trienedial (234 g, 1.43 mol) in DCM (5 L) wasadded dropwise a solution of 30% by wt. NaOMe (749 mL, 4.00 mol) inmethanol. The reaction mixture was refluxed for 3 hrs. The mixture waspushed through a short column of silica and the solvent was reduced invacuo. The residue was redissolved in EtOH (3 L) and heated to refluxfor 3 hrs. Cooled and filtered. The solid was washed with MeOH (100mL×3) then diethyl ether (100 mL) and dried to give 250 g of orangepowder (45%) ¹H NMR (300 Hz, CDCl₃) δ 7.28 (s, 1H, CH), 7.26 (s, 1H,CH), 6.60 (m, 8H, CH), 4.23 (q, 4H, CH₂), 1.98 (s, 6H, CH₃), 1.53 (s,6H, CH₃), 1.25 (t, 6H, CH₃).

Example 17 Preparation of2,6,11,15-Tetramethyl-hexadeca-2,4,6,8,10,12,14-heptaene-1,16-diol

Raw Materials FW Quantity Used Moles2,6,11,15-Tetramethyl-hexadeca-2,4,6,8,10,12,14- 384.51  200 g 0.52 molheptaenedioic acid diethyl ester Methylene chloride 3000 mLDiisobutylaluminum hydride-(1.5 M, Toluene) 142.22 1533 mL 2.30 mol

To a solution of2,6,11,15-tetramethyl-hexadeca-2,4,6,8,10,12,14-heptaenedioic aciddiethyl ester (200 g, 0.52 mol) in 3000 mL of DCM was added dropwise asolution of diisobutylaluminum hydride in toluene (1.5 M, 1533 mL, 2.30mol) at −78° C. The mixture was stirring at 0° C. for 2 h. 100 mL ofwater was added the 200 ml of 2N NaOH was added to quench the reaction.The suspension was filtered off and solid was washed by a large amountof THF. The combined organic layer were dried over Na₂SO₄ and evaporatedto give 133.16 g (85%) brown solid. ¹H NMR (300 Hz, CDCl₃) δ 6.41 (m,10H, CH), 4.16 (s, 4H, CH₂), 1.95 (m, 12H, CH₃)

Example 18 Preparation of2,6,11,15-Tetramethyl-hexadeca-2,4,6,8,10,12,14-heptaenedial

Raw Materials FW Quantity Used Moles2,6,11,15-Tetramethyl-hexadeca-2,4,6,8,10,12,14- 300.44  50 g 0.166 molheptaene-1,16-diol Manganese dioxide  86.94 500 g  5.75 mol Methylenechloride 3000 L

To a suspension of2,6,11,15-tetramethyl-hexadeca-2,4,6,8,10,12,14-heptaene-1,16-diol (50g, 0.166 mol) in 3000 mL of DCM was added portionwise manganese dioxide(500 g, 5.75 mol) at room temperature. The mixture was After heated toreflux for 2 h, the solid was filtered via celite and washed withCH₂Cl₂. The solvent was removed under reduced pressure to give 36 g ofpure product (73%). ¹H-NMR (300 Hz DMSO-d₆) δ 9.42 (s, 2H, CHO), 7.18(s, 1H, CH), 7.16 (s, 1H, CH), 6.93 (m, 6H, CH), 2.01 (s, 6H, CH₃), 1.82(s, 6H, CH₃).

Example 19 Preparation of(S)-(−)-4-Hydroxy-3-methoxy-2,6,6-trimethyl-cyclohex-2-enone

To a solution of (1S,2S)-N-p-toluenesulfonyl-1,2-diphenylethylenediamine(26.8 mg, 0.073 mmol) in Argon sparged 2-propanol (10 mL) was addeddichloro(p-cymene)ruthenium(II)dimer (11.2 mg, 0.018 mmol). Thesuspension was heated to 80° C. for 30 min during which time the solidswent into solution. The reaction was cooled to room temperature, asolution of 1 (670 mg, 3.67 mmol) in degassed 2-propanol (15 mL) wasadded followed by 0.1 M KOH in 2-propanol (1.8 mL) and then stirredovernight. TLC analysis (1:1 ethyl acetate:hexanes) showed the reactionwas complete so the reaction was neutralized with aq. citric acid,filtered through a small pad of silica gel and then concentrated undervacuum. Purification by column chromatography (silica gel, 20:80 ethylacetate:hexanes to 40:60 ethyl acetate:hexanes over 30 min) providedcompound 2 (589 mg, 87%) as a waxy solid.

Example 20 Preparation of(S)-2,2,4,6,6-Pentamethyl-7,7a-dihydro-6H-benzo[1,3]dioxol-5-one

Compound 2 (587 mg, 3.18 mmol) was dissolved in acetone (5 mL),2,2-dimethoxypropane (10 mL) and water (0.15 mL). p-Toluenesulfonic acidmonohydrate (30 mg, 0.157 mmol) was added and the reaction was heated toreflux. After one hour the reaction had only gone 10% so more water(0.15 mL) was added and the reflux was continued. The reaction wasmonitored every hour and more water (0.15 mL) was added until a total of0.75 mL had been added. At this point the reaction was cooled andallowed to stir over night. The next morning all the enol ether had beenhydrolyzed so the reaction was heated to reflux for 1 hour to form theacetonide then cooled and quenched with saturated aq. sodium bicarbonate(0.2 mL). The volatile solvents were removed under reduced pressure thenthe reaction was partitioned between ethyl acetate and water thenextracted with ethyl acetate, dried over sodium sulfate, filtered andconcentrated under vacuum. Purification by column chromatography (silicagel, 15:85 ethyl acetate:hexanes to 25:75 ethyl acetate:hexanes over 20column volumes) provided compound 3 (537 mg, 80%) as an oil. ¹H NMR(CDCl₃) δ 4.88 (m, 1H), 2.20 (dd, J=11.5 Hz, J=5.5 Hz, 1H), 1.85 (dd,J=11.5 Hz, J=11.5 Hz, 1H), 1.69 (s, 3H), 1.63 (s, 3H), 1.56 (s, 3H),1.19 (s, 3H), 1.16 (s, 3H); ESI, m/z 211 [M+H]⁺, 98.2% ee by HPLC.

HPLC Conditions:

Chiral method

Mobile Phase 95:5 heptane:2-propanol

Column: CHIRALCEL OD column, 4.6 mm×250 mm, 10 um. Part #14625

Flow: 1 mL/min

Detection: UV@254 nm

Example 21 Preparation of Epoxyketoisophorone

A buffer may be substituted for the controlled base feed and the pHcontroller as described here. To a 500 ml 3-neck Morton flask fittedwith a bottom outlet, an addition funnel, a magnetic stirrer and athermometer were charged 30 g 5 wt % aqueous sodium bicarbonate, 30 g 5wt. % aqueous sodium carbonate, and 20 g keto-isophorone (0.132 mole).To the stirred mixture was added dropwise over one hour whilemaintaining the temperature between 20 and 25° C. with water-ice bathcooling 15 g 35% hydrogen peroxide (0.165 mole) and the mixture stirredan additional three hours. TLC (e.g., ethyl acetate; heptane 30:70 v/v,silica, iodine visualization, ketoisophorone Rf 0.70,epoxyketoisophorone Rf 0.77) showed complete conversion. The mixture wasallowed to separate, the organic phase retained and the aqueousextracted three times, each time with 100 ml dichloromethane. Thecombined organic and dichloromethane phases were then washed with 50 ml5 wt % sodium bisulfite solution then with 50 ml 20 wt % sodium chloridesolution and the solution dried over anhydrous sodium sulfate. Thefiltered solution was then concentrated in vacuo on a rotovac to furnish19.7 g epoxyketoisophorone. Yield is estimated at 89%. NMR of thisproduct showed it to be >95% pure. ¹H NMR: 1.08 (s, 3H), 1.3 (s, 3H),1.55 (s, 3H), 2.26 (d, j=17, 1H), 3.05 (d, j=17, 1H), 3.52 (s, 1H).

Example 22 Preparation of 3-Hydroxyketoisophorone

The epoxyketoisophorone product was converted to 3-hydroxyketoisophrone.To a 500 ml round bottom flask equipped with an addition funnel, athermometer, and a magnetic stirrer were charged 30 ml water and 19.6 gepoxyketoisophorone and the mixture stirred while adding dropwise overone hour 18 ml 28 wt % sodium hydroxide solution while keeping thetemperature between 30 and 35° C. with a water ice cooling bath. Theyellow mixture was stirred another two hours, cooled to room temperaturethen acidified by dropwise addition to pH I with 37% hydrochloric acidduring which a solid precipitated. The slurry was stirred for one hour,then filtered over paper, washed to neutrality with water, then dried at50° C. and 26 inches vacuum with a nitrogen purge to furnish 17.6 g3-hydroxyketoisophorone as a yellowish solid. The yield is estimated at90%. mp 137-139 (lit. 141-143).

Example 23 Preparation of 3-Methoxyketoisophorone

0.17 g epoxyketoisophorone (1.01 mmole) was dissolved in 2 mL drymethanol under an argon atmosphere. Sodium methoxide was added to thereaction causing the reaction to darken, after an hour at roomtemperature the reaction was heated to 50° C. The solvents were removedunder reduced pressure, the reaction was worked up with water andmethylene chloride. The methylene chloride phase was extracted with twoportions of a sodium chloride solution and dried over sodium sulphate.The product resulted as a yellow oil (128 mg) with which the NMR spectrawas consistent with the desired product.

Example 24 Preparation of 3-Methoxyketoisophorone

To a 3-neck round bottom flask fitted with a heating mantle, an additionfunnel, a magnetic stirrer, and a reflux condenser were charged 1.68 g3-hydroxyketoisophorone (10 mmole) and 10 mL methanol and 11 mL 1 Nsodium hydroxide and the mixture stirred to furnish a yellow solution.To the solution was added dropwise 1.50 g dimethylsulfate which causedclouding. The resulting mixture was stirred vigorously for 2 hours at20° C. then warmed to reflux. The homogeneous solution was held atreflux for 4 hours. TLC showed the reaction to be incomplete with nochange after another 2 hours. On cooling the reaction mixture wascombined with 25 ml water then extracted three times, each time with 50ml dichloromethane. The combined dichloromethane phases were extractedwith 25 ml 5 wt % sodium carbonate and 25 ml 20 wt % sodium chloridethen dried over anhydrous sodium sulfate. The filtered solution wasstripped of solvent in a rotovac to 50° C. and 26 inches vacuum tofurnish a straw colored oil of 1.2 g 3-methoxyketoisophorone. Yield isestimated at 70%. NMR of the product showed it to be >90% pure. ¹H NMR:1.25 (s, 6H), 1.90 (s, 3H), 2.70 (s, 2H), 4.00 (s, 3H).

Example 25 Preparation of 3-Methoxyketoisophorone

0.17 g 3-hydroxyketoisophorone (1.01 mmole) was dissolved in 3 mLmethanol at 0° C. Diazomethane in ether was added dropwise to thesolution to control foaming and spattering. Addition was continued untila yellow color persisted (˜8 mL). Reaction was allowed to continue forone hour, and solvents removed. A yellow oil (186 mg) resulted with anNMR consistent with the desired product.

Example 26 Preparation of 3-Methoxyketoisophorone

0.2 g 3-hydroxyketoisophorone (1.19 mmole) was dissolved in methanol.0.8 g trimethyl orthoformate and 0.04 g trifluoroacetic acid were addedto the solution. The reaction was heated to 50° C.

Example 27 Preparation of 3-Methoxyketoisophorone

0.107 g epoxyketoisophorone (0.64 mmole) was dissolved in 1.0 mLmethanol under an argon atmosphere. Trimethyl orthoformate andtrifluoroacetic acid were added to the solution. The reaction was heatedto 50° C. and allowed to stir overnight.

Example 28 Preparation of 3-Methoxyketoisophorone

0.5 g 3-hydroxyketoisophorone (2.98 mmole) was dissolved in 2 mL drypyridine and 9 mL methylene chloride under an argon atmosphere. MesClwas added in one portion and the reaction was stirred overnight. Thereaction was stripped of solvents, and methanol under argon was added(the precipitates were not completely soluble). Sodium methoxide wasadded resulting in a dark red color and the reaction was stirred at roomtemperature for six hours. The reaction was checked by TLC, the productwas present in apparently low yields.

Example 29 Preparation of 4(S)-Hydroxy-ketoisophorone

To a 50 ml round bottom flask fitted magnetic with a stirrer and aseptum with Argon purge was charged 10 ml isopropanol and 11.2 mgdichloro (p-cymene) ruthenium dimer and 26.8 mg 1S,2S(+)-N-p-luenesulfonyl, 1,2-diphenylethylenediamine and the mixtureheated to 80° C. for thirty minutes then cooled to 20° C. To the mixturewas charged 670 mg 3-methoxyketoisophorone in degassed 15 ml isopropanoland 1.8 ml 0.1 M potassium hydroxide in isopropanol and the reactionmixture stirred overnight. The reaction mixture was neutralized byadding a solution of 35 mg citric acid in 1 ml water, the mixturefiltered through a small pad of silica gel, them stripped to dryness ona rotovac. The residue was chromatographed over 40 g silica gel using agradient of ethyl acetate-hexanes 20:80 to 40:60 v/v. On concentrationof fractions and stripping in vacuo was obtained 589 mg4-hydroxyketoisophorone as a white crystalline solid. Yield wasestimated at 87%. 1H NMR: 1.10 (s, 3H), 1.22 (s, 3H), 1.75 (s, 3H), 1.9(m, 1H), 2.2 (d,d, 1H) 4.0 (s, 3H), 4.7 (m, 1H).

Example 30 Preparation of 4-Hydroxy-ketoisophorone

70 mg 3-methoxyketoisophorone (0.38 mmole) was dissolved in methanol (2mL) under an argon atmosphere. Sodium borohydride (50 mg) was added tothe reaction in one portion and the reaction was stirred at roomtemperature for 0.5 hours. Solvents were removed under reduced pressureand worked up with water (0.5 mL) and methylene chloride (2.0 mL).Methylene chloride fraction was dried over sodium sulfate and thesolvent removed under reduced pressure. A colorless oil resulted (39mg).

Example 31 Preparation of 4-Hydroyxketoisophorone acetone ketal

To a 50 ml round bottom flask fitted with a reflux condenser and amagnetic stirrer were charged 587 mg 4-hydroxyketoisophorone and 5 mlacetone and 10 ml 2,2-dimethoxypropane and 30 mg p-toluenesulfonic acidhydrate and 150 mg water and the mixture heated to reflux. At intervalsof two hours an additional 150 mg water were added each time and afterthe fourth addition reflux continued for an additional two hours. Thecooled reaction mixture was neutralized by addition of 0.2 ml saturatedsodium bicarbonate solution then stripped in vacuo to near dryness. Theresidue was extracted with ethyl acetate and water, the organic phasedried with sodium sulfate then concentrated in vacuo. The residue waschromatographed on 40 g silica gel eluting with ethyl acetate-hexanes15:85 to 25:75. The combined and stripped product fractions furnished537 mg ketal as an oil which later crystallized. The yield is estimatedat 80%. Chiral HPLC showed an enantiomeric excess of 98%. 1H NMR: 1.18(s, 3H), 1.20 (s, 3H), 1.55 (s, 3H), 1.63 (s, 3H), 1.70 (s, 3H), 1.85(d,d, 1H), 2.20 (d, 1H), 4.90 (m, 1H).

Example 32 Bulk Chromatographic Separation of the DiastereomericDicamphanic Acid Ester(s) of Astaxanthin

Bulk chromatographic separation of the diastereomeric dicamphanic acidester(s) of synthetic astaxanthin at preparative chromatography scalewas performed to subsequently make gram-scale quantities of eachstereoisomer of disodium disuccinate ester astaxanthin. A total of 135 gof astaxanthin dicamphanate esters (ASTA-DCE) prepared by derivatizationof racemic astaxanthin with (−)-camphanic acid chloride werefractionated by preparative HPLC (using a 77 mm i.d. 25 cm column formedby packing 550 g of 10 μm Kromasil 60 Å silica; Eka Chemicals, Marietta,Ga.) into a Varian RamPak column packing station. After the dry columnpacking material was mixed with 1200 mL of toluene/2-propanol (50/50)and the resulting slurry was transferred to the 77 mm i.d. columnpacking chamber, the column bed was formed using the dynamic axialcompression of the RamPak unit. The packing solvent was flushed from thecolumn bed for 50 min at a flow rate of 150 mL/min using the preparativeHPLC mobile phase consisting of 95% toluene and 5% methyl ethyl ketone(MEK). The preparative HPLC system consisted of a Waters Prep 4000solvent delivery system and a Waters model 486 variable UV detectorfitted with a prep cell (3 mm path length).

Sample solution was injected directly through the pump, detection was at580 nm, and the chromatogram was recorded on a strip chart recorder. Atthe preparative flow rate of 280 mL/min, the system backpressure was 840psi. The laboratory was equipped with yellow lights, and the windowswere covered to avoid any effects of light on the sample. A samplesolution for preparative HPLC was prepared by dissolving 30 g ofASTA-DCE in 90 mL of methylene chloride and diluting the solution with210 mL of toluene. A portion of the resulting solution (272 mL) wasfurther diluted with 688 mL of preparative HPLC mobile phase to generatethe sample solution that was subsequently injected onto the preparativeHPLC system. The preparative HPLC injection consisted of pumping 120 mLof this ASTA-DCE sample solution (3.4 g of ASTA-DCE) through the pumpand onto the preparative column. The preparative loading was selected tooptimize sample throughput, and the resulting chromatogram consisted ofthree slightly overlapping peaks with the 3R,3′R ester eluting at 14min, the meso-(3R,3′S) ester at 16.5 min, and the 3S,3′S ester at 21.5min. To take advantage of the blank section of the chromatogram for thefirst 10 min, subsequent injections were made 20 min into the previousrun at the valley between the meso and 3S,3′S peaks. Heart cuts of eachof the three peaks were collected in addition to the mixed fractions atthe overlap of the 3R,3′R/meso and the meso/3S,3′S peaks.

A total of 40 preparative injections were processed using 84 L of mobilephase. Thirty-six (36) L of effluent were collected among the fivefractions. The preparative system was flushed with 100 mL of methylenechloride approximately every 6-8 injections or whenever thechromatographic separation deteriorated due to effects from mixing withmobile phase in the pump heads during the injection process. Purifiedmaterials were recovered by removing the solvents in a rotary evaporatorprotected from light to afford 25.4 g of 3R,3′R ester, 47.8 g ofmeso-(3R,3′S) ester, and 24.9 g of 3S,3′S ester. The purifiedastaxanthin dicamphanate esters were saponified to afford 8.5 g (79.8%purity by HPLC) of 3R,3′R-astaxanthin, 18.2 g (90.1% purity by HPLC) ofmeso-astaxanthin, and 9.4 g (82.0% purity by HPLC) of3S,3′S-astaxanthin. The major impurities of the saponification reactionwere the 13- and 9-cis isomers of astaxanthin, identified by HPLC. Thecis-isomers were thermally isomerized to all-trans by refluxing inheptane to afford 8.5 g (87.3% purity by HPLC) of 3R,3′R-astaxanthin,18.2 g (92.5% purity by HPLC) of meso-astaxanthin, and 9.4 g (86.8%purity by HPLC) of 3S,3′S-astaxanthin.

Example 34 General Preparation of Lycophyll 2H

Crocetindialdehyde (238) was obtained from SynChem, Inc. (Des Plaines,Ill.) as a brick-red solid and was used without further purification.Lycopene was obtained from ChromaDex (Santa Ana, Calif.) as a red solidand was used without further purification. Acetic acid3,7-dimethyl-8-oxo-octa-2,6-dienyl ester (230a) (Liu and Prestwich 2002)was synthesized by literature procedures from commercially availablegeranyl acetate (228a). All other reagents and solvents used werepurchased from Acros Organics (Morris Plains, N.J.) and Sigma-Aldrich(St. Louis, Mo.) and were used without further purification. Allreactions were performed under a nitrogen atmosphere. All flashchromatographic purifications were performed on Natland InternationalCorporation 230-400 mesh silica gel using indicated solvents. LC/MS(APCI and ESI+modes) were recorded on an Agilent 1100 LC/MSD VL system;column: Zorbax Eclipse XDB-C18 Rapid Resolution (4.6×75 mm, 3.5 μm);temperature: 25° C.; flow rate: 1.0 mL/min.; mobile phase (A=0.025% TFAin H₂O, B=0.025% TFA in acetonitrile). Gradient program (forintermediates 230a-236a and 216a): 70% A/30% B (start), step gradient to50% B over 5 minutes, step gradient to 100% B over 1.3 minutes, hold at100% B over 4.9 minutes. Gradient program (for intermediates 218a, 2H):70% A/30% B (start), step gradient to 50% B over 5 minutes, stepgradient to 98% B over 3.3 minutes, hold at 98% B over 16.9 minutes.All-trans lycophyll was obtained from crude material using a Waters 996Photo Diode Array detector, Millipore 600E System Controller and Waters717 Autosampler; column: YMC C30 Carotenoid S-5, (10×250 mm, 5 μmcolumn); temperature: 25° C.; flow rate: 4.7 mL/min; mobile phase(A=methanol (MeOH), B=methyl-t-butyl ether (MTBE)) Gradient program: 60%A/40% B (start), step gradient to 80% A over 1 minute, hold at 80% Aover 119 minutes. Fractions were collected from 55-66 minutes. Fractionanalysis was performed on a YMC C30 Carotenoid S-5, (4.6×250 mm, 5 μmcolumn). Proton nuclear magnetic resonance (NMR) spectra were obtainedon a Varian Unity INOVA 500 spectrometer operating at 500.111 MHz(megahertz). Electronic absorption spectra were recorded on a Cary 50Bio UV-Visible spectrophotometer.

Example 35 Preparation of 8-Acetoxy-2,6-dimethyl-octa-2,6-dienoic acid(232a)

To a solution of aldehyde 230a (19.5 g, 92.7 mmol) in 300 mL oftert-butyl alcohol was added 2-methyl-2-butene (98.0 mL, 925 mmol). Tothis was added a solution of sodium dihydrogen phosphate (44.5 g, 371mmol) in 300 mL of water. Sodium chlorite (33.6 g, 371 mmol) was addedin several portions. The resulting mixture was rapidly stirred overnightat room temperature. Ethyl acetate was added and the aqueous layer wasacidified to pH 3 by addition of 1 M HCl. The organic layer wasseparated, and the aqueous layer was extracted with ethyl acetate (3×200mL). The combined organic extracts were washed with brine, dried overMgSO₄, and reduced to dryness in vacuo. The crude product (27.4 g, 121mmol, >100% yield) was used in the next step without furtherpurification: ¹H NMR (500 MHz, CDCl₃) δ: 6.84(t of q, J=7.25 Hz, J=1.50Hz, 1H, ═CH), 5.34 (t of q, J=7.00 Hz, J=1.50 Hz, 1H, ═CH), 4.56 (d,J=7.00 Hz, 2H, —CH₂O—), 2.31 (q, J=7.50 Hz, 2H, —CH₂—), 2.15 (t, J=7.50Hz, 2H, —CH₂—), 2.03 (s, 3H, —CH₃), 1.81 (s, 3H, —CH₃), 1.70 (s, 3H,—CH₃). LC/MS (ESI): m/z 249 [M+Na]⁺.

Example 36 Preparation of 8-Hydroxy-2,6-dimethyl-octa-2,6-dienoic acid(234a)

To a solution of acid 232a (20.0 g, 88.4 mmol) in 400 mL of methanol wasadded a solution of potassium carbonate (24.4 g, 177 mmol) in 100 mL ofwater. The resulting mixture was vigorously stirred overnight at roomtemperature. The reaction was cooled to 0° C., methylene chloride (200mL) was added, and the aqueous layer was acidified to pH 3 with 1 M HCl.The organic layer was separated, and the aqueous layer was extractedwith methylene chloride (2×200 mL). The combined organic extracts werewashed with brine, dried over MgSO₄, and reduced to dryness in vacuo.The crude product (9.65 g, 52.4 mmol, 59% yield) was used in the nextstep without further purification: ¹H NMR (500 MHz, CDCl₃) δ: 6.86 (t ofq, J=7.25 Hz, J=1.50 Hz, 1H, ═CH), 5.43 (t of q, J=7.00 Hz, J=1.50 Hz,1H, ═CH), 4.16 (d, J=7.00 Hz, 2H, —CH₂O—), 2.33(q, J=7.50 Hz, 2H,—CH₂—), 2.16 (t, J=7.50 Hz, 2H, —CH₂—), 1.83 (s, 3H, —CH₃), 1.68 (s, 3H,—CH₃). LC/MS (ESI): m/z 207 [M+Na]⁺.

Example 37 Preparation of 8-Hydroxy-2,6-dimethyl-octa-2,6-dienoic acidmethyl ester (234b)

To a solution of acid 234a (20.1 g, 109 mmol) in 400 mL of DMF was addeda solution of potassium carbonate (16.6 g, 120 mmol) in 80 mL of water.The resulting mixture was vigorously stirred for several minutes. To themixture was added iodomethane (7.50 mL, 120 mmol) via syringe. Theresulting mixture was vigorously stirred overnight at room temperature.Ethyl acetate (400 mL) and water (400 mL) were added and the aqueouslayer was acidified to pH 3 by addition of 1 M HCl. The organic layerwas separated and the aqueous layer was extracted with ethyl acetate(3×200 mL). The combined organic extracts were washed with water (3×500mL), saturated aqueous sodium carbonate, brine, and dried over MgSO₄.The solvent was removed under reduced pressure and the crude productpurified by flash chromatography (MeOH/CH₂Cl₂, 1:49) to afford methylester 5 as a clear oil (19.4 g, 90% yield): ¹H NMR (500 MHz, CDCl₃) δ:6.72 (t of q, J=7.50 Hz, J=1.50 Hz, 1H, ═CH), 5.43 (t of q, J=6.75 Hz,J=1.50 Hz, 1H, ═CH), 4.16 (d, J=7.00 Hz, 2H, —CH₂O—), 3.73 (s, 3H,—CH₃), 2.31 (q, J=7.50 Hz, 2H, —CH₂—), 2.15 (t, J=7.50 Hz, 2H, —CH₂—),1.83 (s, 3H, —CH₃), 1.69 (s, 3H, —CH₃). LC/MS (ESI): m/z 221 [M+Na]⁺.

Example 38 Preparation of 8-Bromo-2,6-dimethyl-octa-2,6-dienoic acidmethyl ester (236a)

To a 0° C. solution of alcohol 234b (12.9, 64.9 mmol) in 250 mL ofanhydrous tetrahydofuran was added carbon tetrabromide (23.8 g, 71.4mmol) in several portions. The mixture was stirred for a few minutes andthen triphenylphosphine (18.7 g, 71.4 mmol) was added and the mixtureallowed to warm to room temperature and stirred overnight. The solventwas removed under reduced pressure and the resulting residue wassuspended in diethyl ether. The suspension was filtered through a pad ofCelite. After solvent removal under reduced pressure the resulting crudeproduct (contaminated with triphenylphosphine oxide) was used directlyin the next step: ¹H NMR (500 MHz, CDCl₃) δ: 6.61 (t of q, J=7.50 Hz,J=1.50 Hz, 1H, ═CH), δ 47 (t of q, J=8.00 Hz, J=1.50 Hz, 1H, 20=CH),3.92 (d, J=8.50 Hz, 2H, —CH₂Br), 3.63 (s, 3H, —CH₃), 2.22 (q, J=8.00 Hz,2H, —CH₂—), 2.10 (t, J=8.00 Hz, 2H, —CH₂—), 1.75 (d, J=1.00 Hz, 3H,—CH₃), 1.66 (d, J=1.00 Hz, 3H, —CH₃).

Example 39 Preparation of (2,6-Dimethyl-8-octa-2,6-dienoic acid methylester)triphenylphosphonium bromide (216a)

To a solution of bromide 236a (9.20 g, 35.2 mmol) in ethyl acetate (200mL) was added triphenylphosphine (10.2 g, 38.8 mmol). The resultingmixture was vigorously stirred for a few minutes, at which time aninsoluble material began to oil out from the solution, adhering to thesides of the flask. The reaction solution was then decanted into a cleanreaction vessel. This procedure was repeated every 5 to 10 minutes untilno more oily insoluble residue was noted, at which time a white solidstarted to precipitate from the solution. The cloudy mixture was thenstirred overnight at room temperature. The mixture was filtered and thefilter cake was rinsed with ethyl acetate and dried in vacuo to affordphosphonium salt 7 as a white solid (9.60 g, 52% yield). ¹H NMR (500MHz, CDCl₃) δ: 7.88-7.84 (m, 6 arom. H), 7.79-7.75 (m, 3 arom. H),7.68-7.64 (m, 6 arom. H), 6.51 (t of q, J=5.00 Hz, J=1.00 Hz, 1H. ═CH),5.10 (q, J=7.00 Hz, 1H, ═CH), 4.70 (d of d, J=15.0, J=8.00 Hz, 2H,—CH₂PPh₃Br), 3.67 (s, 3H, —CH₃), 2.16 (q, J=7.00 Hz, 2H, —CH₂—), 2.08(t, J=6.00 Hz, 2H, —CH₂—), 1.70 (s, 3H, —CH₃), 1.35 (d, J=4.00 Hz, 3H,—CH₃). LC/MS (ESI): m/z 443 [M]⁺.

Example 40 Preparation of Dimethyl ψ,ψ-Carotene-16,16′-dioate (218a)

To a solution of crocetindialdehyde (238) (0.810 g, 2.74 mmol) and 216a(4.30 g, 8.21 mmol) in toluene (100 mL) was added 1 M LiOMe in MeOH(7.67 mL, 7.67 mmol) via syringe. The resulting mixture was refluxed for24 hours, cooled to room temperature, and then water (100 mL) was added.The organic phase was collected, extracted with water twice, and thendried over anhydrous sodium sulfate. After filtration and removal of thesolvent in vacuo, the resulting residue was purified by flashchromatography (ethyl acetate:toluene, 1:99) to afford dimethyl ester240 as a red solid (1.15 g, 67% yield). LC/MS (APCI): m/z 625 [M+H]⁺.

Example 41 Preparation of ψ,ψ-Carotene-16,16′-diol (10)

To a solution of dimethyl ester 218a (1.14 g, 1.83 mmol) in anhydroustetrahydrofuran (100 mL) at 0° C. was added DIBAL (20% by wt. intoluene) (9.13 mL, 11.0 mmol) via syringe. The mixture was warmed toroom temperature and stirred for one hour. The reaction was quenched bythe sequential addition of H₂O (440 μL), 15% aqueous NaOH (440 μL), andH₂O (1.10 mL). The resulting mixture was stirred for 30 minutes and thendried over anhydrous MgSO₄. After filtration and removal of solvent invacuo, the resulting crude diol 2H (0.39 g, 38%) was used in the nextstep without further purification. ¹H NMR (500 MHz, CDCl₃) δ: 6.63 (d ofd, J=15.0 Hz, J=11.5 Hz, 2H, H11, H11′), 6.63 (d, J=11.0 Hz, 2H, H15,H15′), 6.48 (d of d, J=15.0 Hz, J=11.0 Hz, 2H, H7, H7′), 6.36 (d, J=15.0Hz, 2H, H12, H12′), 6.25 (d, J=15.0 Hz, 2H, H8, H8′), 6.19 (d, J=11.5Hz, 2H, H10, H10′), 5.95 (d, J=11.0 Hz, 2H, H6, H6′), 5.40 (t of q,J=6.50 Hz, J=1.50 Hz, 2H, H2, H2′), 4.00(s, 4H, —CH₂O—), 2.19(t, J=Hz,4H, —CH₂—), 2.16 (t, J=Hz, 4H, —CH₂—), LC/MS (APCI): m/z 569 [M+H]⁺.

Example 42 General Preparation of Lycophyll Derivatives

LC/MS (APCI) and LC/MS (ESI) were recorded on an Agilent 1100 LC/MSD VL,PDA detector system; column: Zorbax Eclipse XDB-C18 Rapid Resolution(4.6×75 mm, 3.5 μm); temperature: 25° C.; flow rate: 1.0 mL/min; mobilephase (% A=0.025% trifluoroacetic acid in H₂O, % B=0.025%trifluoroacetic acid in acetonitrile) Gradient program: 70% A/30% B(start), step gradient to 50% B over 5 min, step gradient to 98% B over8.30 min, hold at 98% B over 25.20 min, step gradient to 30% B over25.40 min. A catalytic amount of trifluoroacetic acid is used in theeluents to improve chromatographic resolution. The presence oftrifluoroacetic acid facilitates the protonation of synthesizedlycophyll dissucinate and diphosphate salts to give the free diacidforms (as represented by the theoretical molecular ions M⁺=768 forlycophyll disuccinate salt and M⁺=728 for lycophyll disphosphate salt).LRMS: + mode; ESI: electrospray chemical ionization, ion collectionusing quadrapole; APCI: atmospheric pressure chemical ionization, ioncollection using quadrapole. Reverse-phase HPLC was performed on aWaters 996 HPLC with PDA detector, Millipore 600E System Controllersystem; column: Zorbax Eclipse XDB-C18 (9.4×250 mm, 5 μm); temperature:25° C.; flow rate: 2.1 mL/min; mobile phase (% A=0.025% trifluoroaceticacid in H₂O, % B=0.025% trifluoroacetic acid in MeOH) Isocratic program:15% A/85% B. ¹H NMR analyses were performed on a Varian spectrometer(300 MHz).

Example 43 Preparation of ψ,ψ-carotenyl 16,16′-disuccinate (222a)

To a solution of lycophyll (2H) (0.10 g, 0.176 mmol) in CH₂Cl₂ (2 mL)was added N,N-diisopropylethylamine (0.613 mL, 3.52 mmol) and succinicanhydride (0.1761 g, 1.76 mmol). The solution was stirred at roomtemperature overnight and then diluted with CH₂Cl₂ and quenched withcold water/1 M HCl (9/1). The aqueous layer was extracted two times withCH₂Cl₂ and the combined organic layer was washed three times with coldwater/1 M HCl (9/1), dried over Na₂SO₄, and concentrated to yielddisuccinate 222a (0.124 g, 92%) as a red hygroscopic solid; LC/MS(APCI): 11.59 min (65.17%), λ_(max) 295 nm (28%), 362 nm (8%), 447 nm(72%), 472 nm (100%), 503 nm (93%), m/z 769 [M+H]⁺ (100%), 668[M−C₄O₃H₄]⁺ (9%), 651 (89%), 533 (30%); 12.13 min (33.69%), λ_(max) 295nm (26%), 362 nm (10%), 447 nm (77%), 472 nm (100%), 503 nm (91%), m/z769 [M+H]⁺ (28%), 651 (24%), 531 (8%), 261 (100%).

Example 44 Preparation of ψ,ψ-carotenyl 16,16′-disuccinate sodium salt(224a)

To a solution of disuccinate 222a (0.124 g, 0.161 mmol) in methanol (3mL) at 0° C. was added dropwise sodium methoxide (25% wt in methanol;0.074 mL, 0.322 mmol). The solution was stirred at room temperatureovernight, then cooled to 0° C., and water was added. The red mixturewas stirred for 5 min at 0° C., and then methanol was removed in vacuo.The red, aqueous solution was lyophilized to afford disuccinate salt224a (0.103 g, 88%) as a red hygroscopic solid; LC/MS (APCI): 11.58 min(71.72%), λ_(max) 295 nm (13%), 362 nm (9%), 447 nm (68%), 472 nm(100%), 503 nm (90%), m/z 769 [M+H]⁺ (100%), 651 (42%), 533 (15%); 12.09min (27.74%), λ_(max) 295 nm (31%), 362 nm (19%), 447 nm (80%), 472 nm(100%), 503 nm (88%), m/z 769 [M+H]⁺ (100%), 669 [M−C₄O₃H₄+H]+(12%), 651(54%), 551 (8%), 533 (11%).

Example 45 Preparation of Tribenzyl phosphite (13)

To a well-stirred solution of phosphorus trichloride (1.7 mL, 19.4 mmol)in Et₂O (430 mL) at 0° C. was added dropwise a solution of triethylamine(8.4 mL, 60.3 mmol) in Et₂O (20 mL), followed by a solution of benzylalcohol (8.1 mL, 77.8 mmol) in Et₂O (20 mL). The mixture was stirred at0° C. for 30 min and then at room temperature overnight. The mixture wasfiltered and the filtrate concentrated to give a colorless oil. Silicachromatography (hexanes/Et₂O/triethylamine, 5.5/1/1%) of the crudeproduct gave 13 (5.68 g, 83%) as a clear, colorless oil that was storedunder N₂ at −20° C.; ¹H NMR (300 MHz, CDCl₃) δ: 7.38 (15H, m), 4.90 (6H,d).

Example 46 Preparation of Dibenzyl phosphoroiodidate (14)

To a solution of tribenzyl phosphite (0.708 g, 2.01 mmol) in CH₂Cl₂ (5mL) at 0° C. was added 12 (0.49 g, 1.93 mmol). The mixture was stirredat 0° C. for 10 min or until the solution became clear and colorless.The solution was then stirred at room temperature for 10 min and useddirectly in the next step.

Example 47 Preparation of Mixture of 16,16′-Benzylphosphoryloxy-ψ,ψ-carotenes (221a,221b,221c,221d)

To a solution of lycophyll (2H) (0.11 g, 0.193 mmol) in CH₂Cl₂ (5 mL)was added pyridine (0.624 mL, 7.72 mmol). The solution was stirred at 0°C. for 5 min and then freshly prepared 14 (1.93 mmol) in CH₂Cl₂ (5 mL)was added dropwise to the mixture at 0° C. The solution was stirred at0° C. for 1 h and then diluted with CH₂Cl₂ and quenched with brine. Theaqueous layer was extracted twice with CH₂Cl₂ and the combined organiclayer was washed once with NaSSO₄, once with brine, then dried overNa₂SO₄ and concentrated. Pyridine was removed from the crude red oil byazeotropic distillation using toluene to yield a mixture ofbenzyl-protected diphosphoric acid lycophyll derivatives221a,221b,221c,221d used in the next step without further purification;LC/MS (ESI) for 221a: 10.15 min (7.73%), λ_(max) 295 nm (21%), 362 nm(16%), 447 nm (72%), 472 nm (100%), 503 nm (87%), m/z 819 [M+H]⁺ (18%),800 [M−H₂O]⁺ (11%), 672 (24%), 531 (10%); LC for 221b: 18.00 min(17.46%), λ_(max) 295 nm (18%), 362 nm (13%), 447 nm (74%), 472 nm(100%), 503 nm (85%); LC for 221c: 20.08 min (20.00%), λ_(max) 295 nm(18%), 362 nm (16%), 447 nm (74%), 472 nm (100%), 503 nm (86%); LC for221d: 22.52 min (54.81%), λ_(max) 295 nm (19%), 362 nm (18%), 447 nm(73%), 472 nm (100%), 503 nm (87%).

Example 48 Preparation of 16,16′-Diphosphoryloxy-ψ,ψ-carotene (221e)

To a solution of a mixture of benzyl-protected diphosphoric acidlycophyll derivatives 221a,221b,221c,221d (0.193 mmol) in CH₂Cl₂ (15 mL)at 0° C. was added dropwise N,O-bis(trimethylsilyl)acetamide (0.479 mL,1.93 mmol) and then bromotrimethylsilane (0.203 mL, 1.54 mmol). Thesolution was stirred at 0° C. for 15 min, quenched with triethylamine,and stirred at 0° C. for 5 min. The red solution was then diluted withCH₂Cl₂, Et₂O, and MeOH (2/1/1), and then concentrated. The resulting redoil was resuspended in a minimum amount of MeOH and the cloudy solutionwas centrifuged to remove insoluble reaction byproducts. The redsupernatant was concentrated to afford a mixture of monophosphate anddiphosphate lycophyll derivatives (254/221e) (1/4) contaminated withexcess reagents, and reaction and decomposition byproducts; LC/MS (ESI)for 221e: 9.10 min (39.24%), λ_(max) 295 nm (31%), 362 nm (18%), 447 nm(74%), 472 nm (100%), 503 nm (88%), m/z 849 (25%), 827 (5%), 368(100%),357 (11%), 317 (52%); 9.25 min (37.83%), λ_(max) 295 nm (31%), 362 nm(18%), 447 nm (75%), 472 nm (100%), 503 nm (89%), m/z 849 (10%), 625(8%), 581(6%), 385 (20%), 368 (100%), 357 (28%); LC/MS (ESI) for254:10.21 min (18.50%), 4a 295 nm (32%), 362 nm (24%), 447 nm (78%), 472nm (100%), 503 nm (89%), m/z 648 M+(9%), 630 [M−H₂O]⁺ (5%), 568 (10%),317 (100%); the crude mixture was subjected to reverse-phase HPLCpurification to give diphosphate 221e (approximately 70% pure; 0.063 g,45%) as a red oil, contaminated with excess reagents, and reaction anddecomposition byproducts; LC/MS (ESI): 9.36 min (4.43%), λ_(max) 295 nm(30%), 362 nm (25%), 447 nm (79%), 472 nm (100%), 503 nm (82%), m/z 849(16%), 619 (7%), 399 (23%), 368 (100%), 357 (10%), 317 (8%); 9.58 min(46.42%), λ_(max) 295 nm (30%), 362 nm (15%), 447 nm (80%), 472 nm(100%), 503 nm (92%), m/z 849 (19%), 619 (5%), 399 (21%), 368 (100%),357 (10%), 317 (9%); 9.67 min (49.15%), λ_(max) 295 nm (28%), 362 nm(12%), 447 nm (77%), 472 nm (100%), 503 nm (95%), m/z 849 (15%), 619(5%), 399 (20%), 368 (100%), 357 (8%), 317 (6%).

Example 49 Preparation of 16,16′-Diphosphoryloxy-ψ,ψ-carotene sodiumsalt (223a)

To a solution of lycophyll diphosphate (221e) (approximately 70% pure;0.04 g, 0.055 mmol) in methanol (2 mL) at 0° C. was added dropwisesodium methoxide (25% wt in methanol; 0.05 mL, 0.22 mmol). The solutionwas stirred at room temperature overnight, then cooled to 0° C., andwater was added. The red mixture was stirred for 5 min at 0° C., andthen methanol was removed in vacuo. The red, aqueous solution waslyophilized to yield diphosphate salt 223a (approximately 50% pure;0.018 g, 43%) as a red hygroscopic solid; LC/MS (ESI): 9.26 min (9.34%),λ_(max) 295 nm (28%), 362 nm (18%), 447 nm (81%), 472 nm (100%), 503 nm(87%), m/z 897 (8%), 392 (100%), 381 (10%); 9.48 min (46.98%), λ_(max)295 nm (29%), 362 nm (15%), 447 nm (80%), 472 nm (100%), 503 nm (91%),m/z 911 (10%), 849 (15%), 399 (87%), 368 (100%); 9.56 min (43.68%),λ_(max) 295 nm (28%), 362 nm (12%), 447 nm (77%), 472 nm (100%), 503 nm(90%), m/z 849 (19%), 827 (5%), 368 (100%), 357 (8%).

In this patent, certain U.S. patents, U.S. patent applications, andother materials (e.g., articles) have been incorporated by reference.The text of such U.S. patents, U.S. patent applications, and othermaterials is, however, only incorporated by reference to the extent thatno conflict exists between such text and the other statements anddrawings set forth herein. In the event of such conflict, then any suchconflicting text in such incorporated by reference U.S. patents, U.S.patent applications, and other materials is specifically notincorporated by reference in this patent.

Further modifications and alternative embodiments of various aspects ofthe invention will be apparent to those skilled in the art in view ofthis description. Accordingly, this description is to be construed asillustrative only and is for the purpose of teaching those skilled inthe art the general manner of carrying out the invention. It is to beunderstood that the forms of the invention shown and described hereinare to be taken as the presently preferred embodiments. Elements andmaterials may be substituted for those illustrated and described herein,parts and processes may be reversed, and certain features of theinvention may be utilized independently, all as would be apparent to oneskilled in the art after having the benefit of this description of theinvention. Changes may be made in the elements described herein withoutdeparting from the spirit and scope of the invention as described in thefollowing claims.

Example 50 Separation of (3S,3′S)-all-E-astaxanthin

Analysis of the stereoisomeric distribution of astaxanthin wasaccomplished using a chiral HPLC column. A Regis Pirkle CovalentD-phenylglycine, 5 Å, 4.6×250 nm chiral HPLC column was used. Thedetector was set at 474 nm. A 10 μL sample was injected into the column.The sample was passed through the column using a mobile phase of 75%Heptane, 24% dichloromethane, and 1% ethanol at a flow rate of 1.5mL/min. Racemic astaxanthin (e.g., 3S,3′S, meso (3R,3′S), and 3R,3′R ina 1:2:1 ratio) was run through the chiral HPLC column and the retentiontime for 3S,3′S (“S,S”)-astaxanthin was 32.763 min, meso-astaxanthin was31.165, and 3R,3′R (“R,R”)-astaxanthin was 29.937. The total run timewas 60 minutes.

In this patent, certain U.S. patents, U.S. patent applications, andother materials (e.g., articles) have been incorporated by reference.The text of such U.S. patents, U.S. patent applications, and othermaterials is, however, only incorporated by reference to the extent thatno conflict exists between such text and the other statements anddrawings set forth herein. In the event of such conflict, then any suchconflicting text in such incorporated by reference U.S. patents, U.S.patent applications, and other materials is specifically notincorporated by reference in this patent.

Further modifications and alternative embodiments of various aspects ofthe invention may be apparent to those skilled in the art in view ofthis description. Accordingly, this description is to be construed asillustrative only and is for the purpose of teaching those skilled inthe art the general manner of carrying out the invention. It is to beunderstood that the forms of the invention shown and described hereinare to be taken as the presently preferred embodiments. Elements andmaterials may be substituted for those illustrated and described herein,parts and processes may be reversed, and certain features of theinvention may be utilized independently, all as would be apparent to oneskilled in the art after having the benefit of this description to theinvention. Changes may be made in the elements described herein withoutdeparting from the spirit and scope of the invention as described in thefollowing claims. In addition, it is to be understood that featuresdescribed herein independently may, in certain embodiments, be combined.

1-108. (canceled)
 109. A method of producing astaxanthin, comprising:contacting a diketone compound having the structure:

where R¹ is alkyl, phenyl, aryl or silyl; with a chiral catalyst, tostereoselectively reduce the ketone to give a hydroxy compound havingthe structure:

performing additional chemical processes to form astaxanthin from thehydroxy compound.
 110. The method of claim 109, wherein the chiralcatalyst comprises metal and an optically active chiral ligand.
 111. Themethod of claim 109, wherein the chiral catalyst comprises ruthenium andan optically active chiral ligand.
 112. The method of claim 109, whereinthe chiral catalyst comprises ruthenium and an optically active amine.113. The method of claim 109, wherein the chiral catalyst comprisesruthenium and an optically active amino acid.
 114. The method of claim109, wherein the chiral catalyst comprises ruthenium and an opticallyactive amine having the structure H₂N—CHPh—CHPh—OH.
 115. The method ofclaim 109, wherein the chiral catalyst comprises ruthenium and anoptically active amine having the structure H₂N—CHMe—CHPh—OH.
 116. Themethod of claim 109, wherein the chiral catalyst comprises ruthenium andan optically active amine having the structure MeHN—CHMe—CHPh—OH. 117.The method of claim 109, wherein the chiral catalyst comprises rutheniumand an optically active amine having the structure TsNH—CHPh—CHPh—NH₂.118. The method of claim 109, wherein performing additional chemicalprocesses to form astaxanthin comprises: converting the dihydroxycompound into a protected ketone having the structure:

where each R¹ is independently alkyl, phenyl, aryl, silyl, or where bothR¹ combine to form a ketal.
 119. The method of claim 118, whereinperforming additional chemical processes to form astaxanthin comprises:converting the protected ketone into an addition product having thestructure:

where R¹ is alkyl, phenyl, aryl silyl, or where both R¹ combine to forma ketal, and R² is


120. The method of claim 119, wherein performing additional chemicalprocesses to form astaxanthin comprises: converting the unsaturatedketone into the compound having the structure:

where R¹ is alkyl, phenyl, aryl or silyl; and R³ is PR⁴ ₃, P(O)R⁴ ₃,SO₂R⁴, or M⁺ where R⁴ is alkyl, phenyl, or aryl and M is Li, Na, orMgBr.
 121. The method of claim 120, wherein performing additionalchemical processes to form astaxanthin comprises: reacting the compoundhaving the structure:

where R¹ is alkyl, phenyl, aryl or silyl; and R³ is PR⁴ ₃, P(O)R⁴ ₃,SO₂R⁴, or M⁺ where R⁴ is alkyl, phenyl, or aryl and M is Li, Na, or MgBrwith a dialdehyde having the structure:

to form astaxanthin.
 122. The method of claim 109, wherein astaxanthinis formed as the 3S, 3′S stereoisomer.
 123. (canceled)
 124. A method ofproducing astaxanthin, comprising: contacting a diketone compound havingthe structure:

where R¹ is alkyl, phenyl, aryl or silyl; with a chiral catalyst, tostereoselectively reduce the ketone to give a hydroxy compound havingthe structure:

performing additional chemical processes to form astaxanthin from thehydroxy compound.
 125. The method of claim 124, wherein astaxanthin isformed as the 3R, 3′R stereoisomer.
 126. The method of claim 124,wherein the chiral catalyst comprises ruthenium and an optically activeamine.
 127. The method of claim 124, wherein the chiral catalystcomprises ruthenium and an optically active amine having the structureH₂N—CHPh—CHPh—OH.
 128. The method of claim 124, wherein the chiralcatalyst comprises ruthenium and an optically active amine having thestructure H₂N—CHMe—CHPh—OH.
 129. The method of claim 124, wherein thechiral catalyst comprises ruthenium and an optically active amine havingthe structure MeHN—CHMe—CHPh—OH.